The formation of a fibrin clot at the site of an injury to the wall of a normal blood vessel is an essential part of the process to stop blood loss after vascular injury. The reactions that lead to fibrin clot formation are commonly described as a cascade, in which the product of each step is an enzyme or cofactor needed for following reactions to proceed efficiently. The entire clotting cascade can be divided into three portions, the extrinsic pathway, the intrinsic pathway, and the common pathway. The extrinsic pathway begins with the release of tissue factor at the site of vascular injury and leads to the activation of factor X. The intrinsic pathway provides an alternative mechanism for activation of factor X, starting from the activation of factor XII. The common pathway consists of the steps linking the activation of factor X to the formation of a multimeric, cross-linked fibrin clot. Each of these pathways includes not only a cascade of events that generate the catalytic activities needed for clot formation, but also numerous positive and negative regulatory events.
View original pathway at:Reactome.
Kisiel W.; ''Human plasma protein C: isolation, characterization, and mechanism of activation by alpha-thrombin.''; PubMedEurope PMCScholia
Gailani D, Ho D, Sun MF, Cheng Q, Walsh PN.; ''Model for a factor IX activation complex on blood platelets: dimeric conformation of factor XIa is essential.''; PubMedEurope PMCScholia
de Maat S, Björkqvist J, Suffritti C, Wiesenekker CP, Nagtegaal W, Koekman A, van Dooremalen S, Pasterkamp G, de Groot PG, Cicardi M, Renné T, Maas C.; ''Plasmin is a natural trigger for bradykinin production in patients with hereditary angioedema with factor XII mutations.''; PubMedEurope PMCScholia
Mann KG, Butenas S, Brummel K.; ''The dynamics of thrombin formation.''; PubMedEurope PMCScholia
Hagen FS, Gray CL, O'Hara P, Grant FJ, Saari GC, Woodbury RG, Hart CE, Insley M, Kisiel W, Kurachi K.; ''Characterization of a cDNA coding for human factor VII.''; PubMedEurope PMCScholia
Kothari H, Pendurthi UR, Rao LV.; ''Analysis of tissue factor expression in various cell model systems: cryptic vs. active.''; PubMedEurope PMCScholia
Pieters J, Lindhout T, Hemker HC.; ''In situ-generated thrombin is the only enzyme that effectively activates factor VIII and factor V in thromboplastin-activated plasma.''; PubMedEurope PMCScholia
Ni F, Konishi Y, Frazier RB, Scheraga HA, Lord ST.; ''High-resolution NMR studies of fibrinogen-like peptides in solution: interaction of thrombin with residues 1-23 of the A alpha chain of human fibrinogen.''; PubMedEurope PMCScholia
Wen DZ, Dittman WA, Ye RD, Deaven LL, Majerus PW, Sadler JE.; ''Human thrombomodulin: complete cDNA sequence and chromosome localization of the gene.''; PubMedEurope PMCScholia
Bock SC, Wion KL, Vehar GA, Lawn RM.; ''Cloning and expression of the cDNA for human antithrombin III.''; PubMedEurope PMCScholia
Harpel PC, Lewin MF, Kaplan AP.; ''Distribution of plasma kallikrein between C-1 inactivator and alpha 2-macroglobulin in plasma utilizing a new assay for alpha 2-macroglobulin-kallikrein complexes.''; PubMedEurope PMCScholia
Foster D, Davie EW.; ''Characterization of a cDNA coding for human protein C.''; PubMedEurope PMCScholia
Yoshitake S, Schach BG, Foster DC, Davie EW, Kurachi K.; ''Nucleotide sequence of the gene for human factor IX (antihemophilic factor B).''; PubMedEurope PMCScholia
Meier HL, Pierce JV, Colman RW, Kaplan AP.; ''Activation and function of human Hageman factor. The role of high molecular weight kininogen and prekallikrein.''; PubMedEurope PMCScholia
Roehrig S, Straub A, Pohlmann J, Lampe T, Pernerstorfer J, Schlemmer KH, Reinemer P, Perzborn E.; ''Discovery of the novel antithrombotic agent 5-chloro-N-({(5S)-2-oxo-3- [4-(3-oxomorpholin-4-yl)phenyl]-1,3-oxazolidin-5-yl}methyl)thiophene- 2-carboxamide (BAY 59-7939): an oral, direct factor Xa inhibitor.''; PubMedEurope PMCScholia
Sottrup-Jensen L, Stepanik TM, Kristensen T, Wierzbicki DM, Jones CM, Lønblad PB, Magnusson S, Petersen TE.; ''Primary structure of human alpha 2-macroglobulin. V. The complete structure.''; PubMedEurope PMCScholia
Suzuki K, Nishioka J, Kusumoto H, Hashimoto S.; ''Mechanism of inhibition of activated protein C by protein C inhibitor.''; PubMedEurope PMCScholia
Chiu AT, Mousa SA, Pease LJ, Roscoe WA, Bozarth JM, Reilly TM, Smith RD, Timmermans PB.; ''Inhibition of the thrombin-platelet reactions by DuP 714.''; PubMedEurope PMCScholia
Lin Y, Harris RB, Yan W, McCrae KR, Zhang H, Colman RW.; ''High molecular weight kininogen peptides inhibit the formation of kallikrein on endothelial cell surfaces and subsequent urokinase-dependent plasmin formation.''; PubMedEurope PMCScholia
Ruf W, Kalnik MW, Lund-Hansen T, Edgington TS.; ''Characterization of factor VII association with tissue factor in solution. High and low affinity calcium binding sites in factor VII contribute to functionally distinct interactions.''; PubMedEurope PMCScholia
Orfeo T, Brufatto N, Nesheim ME, Xu H, Butenas S, Mann KG.; ''The factor V activation paradox.''; PubMedEurope PMCScholia
Chung DW, Fujikawa K, McMullen BA, Davie EW.; ''Human plasma prekallikrein, a zymogen to a serine protease that contains four tandem repeats.''; PubMedEurope PMCScholia
Foster DC, Sprecher CA, Holly RD, Gambee JE, Walker KM, Kumar AA.; ''Endoproteolytic processing of the dibasic cleavage site in the human protein C precursor in transfected mammalian cells: effects of sequence alterations on efficiency of cleavage.''; PubMedEurope PMCScholia
Gilbert GE, Arena AA.; ''Activation of the factor VIIIa-factor IXa enzyme complex of blood coagulation by membranes containing phosphatidyl-L-serine.''; PubMedEurope PMCScholia
Gustafsson D, Antonsson T, Bylund R, Eriksson U, Gyzander E, Nilsson I, Elg M, Mattsson C, Deinum J, Pehrsson S, Karlsson O, Nilsson A, Sörensen H.; ''Effects of melagatran, a new low-molecular-weight thrombin inhibitor, on thrombin and fibrinolytic enzymes.''; PubMedEurope PMCScholia
Bach R, Gentry R, Nemerson Y.; ''Factor VII binding to tissue factor in reconstituted phospholipid vesicles: induction of cooperativity by phosphatidylserine.''; PubMedEurope PMCScholia
Rao LV, Pendurthi UR.; ''Regulation of tissue factor coagulant activity on cell surfaces.''; PubMedEurope PMCScholia
Lottspeich F, Kellermann J, Henschen A, Foertsch B, Müller-Esterl W.; ''The amino acid sequence of the light chain of human high-molecular-mass kininogen.''; PubMedEurope PMCScholia
Pipe SW, Saenko EL, Eickhorst AN, Kemball-Cook G, Kaufman RJ.; ''Hemophilia A mutations associated with 1-stage/2-stage activity discrepancy disrupt protein-protein interactions within the triplicated A domains of thrombin-activated factor VIIIa.''; PubMedEurope PMCScholia
Saenko EL, Scandella D, Yakhyaev AV, Greco NJ.; ''Activation of factor VIII by thrombin increases its affinity for binding to synthetic phospholipid membranes and activated platelets.''; PubMedEurope PMCScholia
Ivanov I, Matafonov A, Sun MF, Mohammed BM, Cheng Q, Dickeson SK, Kundu S, Verhamme IM, Gruber A, McCrae K, Gailani D.; ''A mechanism for hereditary angioedema with normal C1 inhibitor: an inhibitory regulatory role for the factor XII heavy chain.''; PubMedEurope PMCScholia
Kaufman RJ, Pipe SW, Tagliavacca L, Swaroop M, Moussalli M.; ''Biosynthesis, assembly and secretion of coagulation factor VIII.''; PubMedEurope PMCScholia
Joseph K, Ghebrehiwet B, Peerschke EI, Reid KB, Kaplan AP.; ''Identification of the zinc-dependent endothelial cell binding protein for high molecular weight kininogen and factor XII: identity with the receptor that binds to the globular "heads" of C1q (gC1q-R).''; PubMedEurope PMCScholia
Pixley RA, Schapira M, Colman RW.; ''The regulation of human factor XIIa by plasma proteinase inhibitors.''; PubMedEurope PMCScholia
DiScipio RG, Davie EW.; ''Characterization of protein S, a gamma-carboxyglutamic acid containing protein from bovine and human plasma.''; PubMedEurope PMCScholia
Bouma BN, Griffin JH.; ''Human blood coagulation factor XI. Purification, properties, and mechanism of activation by activated factor XII.''; PubMedEurope PMCScholia
Esmon CT.; ''The roles of protein C and thrombomodulin in the regulation of blood coagulation.''; PubMedEurope PMCScholia
Lawson JH, Mann KG.; ''Cooperative activation of human factor IX by the human extrinsic pathway of blood coagulation.''; PubMedEurope PMCScholia
Degen SJ, Davie EW.; ''Nucleotide sequence of the gene for human prothrombin.''; PubMedEurope PMCScholia
Kerbiriou DM, Griffin JH.; ''Human high molecular weight kininogen. Studies of structure-function relationships and of proteolysis of the molecule occurring during contact activation of plasma.''; PubMedEurope PMCScholia
Ratnoff OD, Pensky J, Ogston D, Naff GB.; ''The inhibition of plasmin, plasma kallikrein, plasma permeability factor, and the C'1r subcomponent of the first component of complement by serum C'1 esterase inhibitor.''; PubMedEurope PMCScholia
Di Scipio RG, Hermodson MA, Yates SG, Davie EW.; ''A comparison of human prothrombin, factor IX (Christmas factor), factor X (Stuart factor), and protein S.''; PubMedEurope PMCScholia
Modderman PW, Admiraal LG, Sonnenberg A, von dem Borne AE.; ''Glycoproteins V and Ib-IX form a noncovalent complex in the platelet membrane.''; PubMedEurope PMCScholia
Baglia FA, Walsh PN.; ''Thrombin-mediated feedback activation of factor XI on the activated platelet surface is preferred over contact activation by factor XIIa or factor XIa.''; PubMedEurope PMCScholia
Simioni P, Tormene D, Tognin G, Gavasso S, Bulato C, Iacobelli NP, Finn JD, Spiezia L, Radu C, Arruda VR.; ''X-linked thrombophilia with a mutant factor IX (factor IX Padua).''; PubMedEurope PMCScholia
Mertens K, Cupers R, Van Wijngaarden A, Bertina RM.; ''Binding of human blood-coagulation Factors IXa and X to phospholipid membranes.''; PubMedEurope PMCScholia
Grover SP, Mackman N.; ''Tissue Factor: An Essential Mediator of Hemostasis and Trigger of Thrombosis.''; PubMedEurope PMCScholia
Shariat-Madar Z, Mahdi F, Schmaier AH.; ''Identification and characterization of prolylcarboxypeptidase as an endothelial cell prekallikrein activator.''; PubMedEurope PMCScholia
Oliver JA, Monroe DM, Roberts HR, Hoffman M.; ''Thrombin activates factor XI on activated platelets in the absence of factor XII.''; PubMedEurope PMCScholia
Mann KG, Kalafatis M.; ''Factor V: a combination of Dr Jekyll and Mr Hyde.''; PubMedEurope PMCScholia
Mohammed BM, Matafonov A, Ivanov I, Sun MF, Cheng Q, Dickeson SK, Li C, Sun D, Verhamme IM, Emsley J, Gailani D.; ''An update on factor XI structure and function.''; PubMedEurope PMCScholia
Kurosawa S, Stearns-Kurosawa DJ, Hidari N, Esmon CT.; ''Identification of functional endothelial protein C receptor in human plasma.''; PubMedEurope PMCScholia
Ichinose A, Hendrickson LE, Fujikawa K, Davie EW.; ''Amino acid sequence of the a subunit of human factor XIII.''; PubMedEurope PMCScholia
Banner DW, D'Arcy A, Chène C, Winkler FK, Guha A, Konigsberg WH, Nemerson Y, Kirchhofer D.; ''The crystal structure of the complex of blood coagulation factor VIIa with soluble tissue factor.''; PubMedEurope PMCScholia
Rawala-Sheikh R, Ahmad SS, Ashby B, Walsh PN.; ''Kinetics of coagulation factor X activation by platelet-bound factor IXa.''; PubMedEurope PMCScholia
Regan LM, Lamphear BJ, Huggins CF, Walker FJ, Fay PJ.; ''Factor IXa protects factor VIIIa from activated protein C. Factor IXa inhibits activated protein C-catalyzed cleavage of factor VIIIa at Arg562.''; PubMedEurope PMCScholia
Lollar P, Hill-Eubanks DC, Parker CG.; ''Association of the factor VIII light chain with von Willebrand factor.''; PubMedEurope PMCScholia
McMullen BA, Fujikawa K, Davie EW.; ''Location of the disulfide bonds in human coagulation factor XI: the presence of tandem apple domains.''; PubMedEurope PMCScholia
Mann KG, Jenny RJ, Krishnaswamy S.; ''Cofactor proteins in the assembly and expression of blood clotting enzyme complexes.''; PubMedEurope PMCScholia
Ghebrehiwet B, Lim BL, Peerschke EI, Willis AC, Reid KB.; ''Isolation, cDNA cloning, and overexpression of a 33-kD cell surface glycoprotein that binds to the globular "heads" of C1q.''; PubMedEurope PMCScholia
Eaton D, Rodriguez H, Vehar GA.; ''Proteolytic processing of human factor VIII. Correlation of specific cleavages by thrombin, factor Xa, and activated protein C with activation and inactivation of factor VIII coagulant activity.''; PubMedEurope PMCScholia
Kaufman RJ, Wasley LC, Dorner AJ.; ''Synthesis, processing, and secretion of recombinant human factor VIII expressed in mammalian cells.''; PubMedEurope PMCScholia
McMullen BA, Fujikawa K, Kisiel W, Sasagawa T, Howald WN, Kwa EY, Weinstein B.; ''Complete amino acid sequence of the light chain of human blood coagulation factor X: evidence for identification of residue 63 as beta-hydroxyaspartic acid.''; PubMedEurope PMCScholia
Turner NA, Moake JL.; ''Factor VIII Is Synthesized in Human Endothelial Cells, Packaged in Weibel-Palade Bodies and Secreted Bound to ULVWF Strings.''; PubMedEurope PMCScholia
Fujikawa K, McMullen BA.; ''Amino acid sequence of human beta-factor XIIa.''; PubMedEurope PMCScholia
Zhang P, Huang W, Wang L, Bao L, Jia ZJ, Bauer SM, Goldman EA, Probst GD, Song Y, Su T, Fan J, Wu Y, Li W, Woolfrey J, Sinha U, Wong PW, Edwards ST, Arfsten AE, Clizbe LA, Kanter J, Pandey A, Park G, Hutchaleelaha A, Lambing JL, Hollenbach SJ, Scarborough RM, Zhu BY.; ''Discovery of betrixaban (PRT054021), N-(5-chloropyridin-2-yl)-2-(4-(N,N-dimethylcarbamimidoyl)benzamido)-5-methoxybenzamide, a highly potent, selective, and orally efficacious factor Xa inhibitor.''; PubMedEurope PMCScholia
Odya CE, Marinkovic DV, Hammon KJ, Stewart TA, Erdös EG.; ''Purification and properties of prolylcarboxypeptidase (angiotensinase C) from human kidney.''; PubMedEurope PMCScholia
Wilcox JN, Smith KM, Schwartz SM, Gordon D.; ''Localization of tissue factor in the normal vessel wall and in the atherosclerotic plaque.''; PubMedEurope PMCScholia
Walz DA, Hewett-Emmett D, Seegers WH.; ''Amino acid sequence of human prothrombin fragments 1 and 2.''; PubMedEurope PMCScholia
Geng Y, Verhamme IM, Messer A, Sun MF, Smith SB, Bajaj SP, Gailani D.; ''A sequential mechanism for exosite-mediated factor IX activation by factor XIa.''; PubMedEurope PMCScholia
Vlot AJ, Koppelman SJ, van den Berg MH, Bouma BN, Sixma JJ.; ''The affinity and stoichiometry of binding of human factor VIII to von Willebrand factor.''; PubMedEurope PMCScholia
McMullen BA, Fujikawa K.; ''Amino acid sequence of the heavy chain of human alpha-factor XIIa (activated Hageman factor).''; PubMedEurope PMCScholia
Fay PJ, Haidaris PJ, Smudzin TM.; ''Human factor VIIIa subunit structure. Reconstruction of factor VIIIa from the isolated A1/A3-C1-C2 dimer and A2 subunit.''; PubMedEurope PMCScholia
Motta G, Rojkjaer R, Hasan AA, Cines DB, Schmaier AH.; ''High molecular weight kininogen regulates prekallikrein assembly and activation on endothelial cells: a novel mechanism for contact activation.''; PubMedEurope PMCScholia
Hill-Eubanks DC, Parker CG, Lollar P.; ''Differential proteolytic activation of factor VIII-von Willebrand factor complex by thrombin.''; PubMedEurope PMCScholia
Komiyama Y, Pedersen AH, Kisiel W.; ''Proteolytic activation of human factors IX and X by recombinant human factor VIIa: effects of calcium, phospholipids, and tissue factor.''; PubMedEurope PMCScholia
Kane WH, Davie EW.; ''Cloning of a cDNA coding for human factor V, a blood coagulation factor homologous to factor VIII and ceruloplasmin.''; PubMedEurope PMCScholia
Kaufman RJ, Wasley LC, Furie BC, Furie B, Shoemaker CB.; ''Expression, purification, and characterization of recombinant gamma-carboxylated factor IX synthesized in Chinese hamster ovary cells.''; PubMedEurope PMCScholia
Laudano AP, Doolittle RF.; ''Studies on synthetic peptides that bind to fibrinogen and prevent fibrin polymerization. Structural requirements, number of binding sites, and species differences.''; PubMedEurope PMCScholia
Ichinose A, McMullen BA, Fujikawa K, Davie EW.; ''Amino acid sequence of the b subunit of human factor XIII, a protein composed of ten repetitive segments.''; PubMedEurope PMCScholia
Schreiber AD, Kaplan AP, Austen KF.; ''Inhibition by C1INH of Hagemann factor fragment activation of coagulation, fibrinolysis, and kinin generation.''; PubMedEurope PMCScholia
Celie PH, Van Stempvoort G, Jorieux S, Mazurier C, Van Mourik JA, Mertens K.; ''Substitution of Arg527 and Arg531 in factor VIII associated with mild haemophilia A: characterization in terms of subunit interaction and cofactor function.''; PubMedEurope PMCScholia
Riewald M, Petrovan RJ, Donner A, Mueller BM, Ruf W.; ''Activation of endothelial cell protease activated receptor 1 by the protein C pathway.''; PubMedEurope PMCScholia
Bhanwra S, Ahluwalia K.; ''The new factor Xa inhibitor: Apixaban.''; PubMedEurope PMCScholia
Sorensen AB, Madsen JJ, Frimurer TM, Overgaard MT, Gandhi PS, Persson E, Olsen OH.; ''Allostery in Coagulation Factor VIIa Revealed by Ensemble Refinement of Crystallographic Structures.''; PubMedEurope PMCScholia
Prandini MH, Reboul A, Colomb MG.; ''Biosynthesis of complement C1 inhibitor by Hep G2 cells. Reactivity of different glycosylated forms of the inhibitor with C1s.''; PubMedEurope PMCScholia
Leytus SP, Chung DW, Kisiel W, Kurachi K, Davie EW.; ''Characterization of a cDNA coding for human factor X.''; PubMedEurope PMCScholia
de Maat S, Clark CC, Boertien M, Parr N, Sanrattana W, Hofman ZLM, Maas C.; ''Factor XII truncation accelerates activation in solution.''; PubMedEurope PMCScholia
Griffin JH, Fernández JA, Gale AJ, Mosnier LO.; ''Activated protein C.''; PubMedEurope PMCScholia
McMullen BA, Fujikawa K, Kisiel W.; ''The occurrence of beta-hydroxyaspartic acid in the vitamin K-dependent blood coagulation zymogens.''; PubMedEurope PMCScholia
Kurachi K, Davie EW.; ''Activation of human factor XI (plasma thromboplastin antecedent) by factor XIIa (activated Hageman factor).''; PubMedEurope PMCScholia
Naito K, Fujikawa K.; ''Activation of human blood coagulation factor XI independent of factor XII. Factor XI is activated by thrombin and factor XIa in the presence of negatively charged surfaces.''; PubMedEurope PMCScholia
Minor C, Tellor KB, Armbruster AL.; ''Edoxaban, a Novel Oral Factor Xa Inhibitor.''; PubMedEurope PMCScholia
Lenting PJ, van Mourik JA, Mertens K.; ''The life cycle of coagulation factor VIII in view of its structure and function.''; PubMedEurope PMCScholia
Shrimpton CN, Borthakur G, Larrucea S, Cruz MA, Dong JF, López JA.; ''Localization of the adhesion receptor glycoprotein Ib-IX-V complex to lipid rafts is required for platelet adhesion and activation.''; PubMedEurope PMCScholia
Mushunje A, Zhou A, Carrell RW, Huntington JA.; ''Heparin-induced substrate behavior of antithrombin Cambridge II.''; PubMedEurope PMCScholia
Graetz TJ, Tellor BR, Smith JR, Avidan MS.; ''Desirudin: a review of the pharmacology and clinical application for the prevention of deep vein thrombosis.''; PubMedEurope PMCScholia
Stangier J, Rathgen K, Stähle H, Gansser D, Roth W.; ''The pharmacokinetics, pharmacodynamics and tolerability of dabigatran etexilate, a new oral direct thrombin inhibitor, in healthy male subjects.''; PubMedEurope PMCScholia
Hakeos WH, Miao H, Sirachainan N, Kemball-Cook G, Saenko EL, Kaufman RJ, Pipe SW.; ''Hemophilia A mutations within the factor VIII A2-A3 subunit interface destabilize factor VIIIa and cause one-stage/two-stage activity discrepancy.''; PubMedEurope PMCScholia
Kane WH, Ichinose A, Hagen FS, Davie EW.; ''Cloning of cDNAs coding for the heavy chain region and connecting region of human factor V, a blood coagulation factor with four types of internal repeats.''; PubMedEurope PMCScholia
Mahdi F, Shariat-Madar Z, Schmaier AH.; ''The relative priority of prekallikrein and factors XI/XIa assembly on cultured endothelial cells.''; PubMedEurope PMCScholia
Gailani D, Broze GJ.; ''Factor XII-independent activation of factor XI in plasma: effects of sulfatides on tissue factor-induced coagulation.''; PubMedEurope PMCScholia
Moreira CR, Schmaier AH, Mahdi F, da Motta G, Nader HB, Shariat-Madar Z.; ''Identification of prolylcarboxypeptidase as the cell matrix-associated prekallikrein activator.''; PubMedEurope PMCScholia
Thim L, Bjoern S, Christensen M, Nicolaisen EM, Lund-Hansen T, Pedersen AH, Hedner U.; ''Amino acid sequence and posttranslational modifications of human factor VIIa from plasma and transfected baby hamster kidney cells.''; PubMedEurope PMCScholia
Baglia FA, Badellino KO, Li CQ, Lopez JA, Walsh PN.; ''Factor XI binding to the platelet glycoprotein Ib-IX-V complex promotes factor XI activation by thrombin.''; PubMedEurope PMCScholia
Bondarenko M, Curti C, Montana M, Rathelot P, Vanelle P.; ''Efficacy and toxicity of factor Xa inhibitors.''; PubMedEurope PMCScholia
Joseph K, Shibayama Y, Ghebrehiwet B, Kaplan AP.; ''Factor XII-dependent contact activation on endothelial cells and binding proteins gC1qR and cytokeratin 1.''; PubMedEurope PMCScholia
Titani K, Kumar S, Takio K, Ericsson LH, Wade RD, Ashida K, Walsh KA, Chopek MW, Sadler JE, Fujikawa K.; ''Amino acid sequence of human von Willebrand factor.''; PubMedEurope PMCScholia
Silverberg M, Dunn JT, Garen L, Kaplan AP.; ''Autoactivation of human Hageman factor. Demonstration utilizing a synthetic substrate.''; PubMedEurope PMCScholia
Li W, Huntington JA.; ''Crystal structures of protease nexin-1 in complex with heparin and thrombin suggest a 2-step recognition mechanism.''; PubMedEurope PMCScholia
Fay PJ, Smudzin TM.; ''Characterization of the interaction between the A2 subunit and A1/A3-C1-C2 dimer in human factor VIIIa.''; PubMedEurope PMCScholia
Mahdi F, Madar ZS, Figueroa CD, Schmaier AH.; ''Factor XII interacts with the multiprotein assembly of urokinase plasminogen activator receptor, gC1qR, and cytokeratin 1 on endothelial cell membranes.''; PubMedEurope PMCScholia
Griffin JH, Cochrane CG.; ''Mechanisms for the involvement of high molecular weight kininogen in surface-dependent reactions of Hageman factor.''; PubMedEurope PMCScholia
Taylor FB, Peer GT, Lockhart MS, Ferrell G, Esmon CT.; ''Endothelial cell protein C receptor plays an important role in protein C activation in vivo.''; PubMedEurope PMCScholia
Broze GJ, Girard TJ, Novotny WF.; ''Regulation of coagulation by a multivalent Kunitz-type inhibitor.''; PubMedEurope PMCScholia
Tan F, Morris PW, Skidgel RA, Erdös EG.; ''Sequencing and cloning of human prolylcarboxypeptidase (angiotensinase C). Similarity to both serine carboxypeptidase and prolylendopeptidase families.''; PubMedEurope PMCScholia
Rapaport SI, Rao LV.; ''The tissue factor pathway: how it has become a "prima ballerina".''; PubMedEurope PMCScholia
Church FC, Noyes CM, Griffith MJ.; ''Inhibition of chymotrypsin by heparin cofactor II.''; PubMedEurope PMCScholia
Lewis SD, Janus TJ, Lorand L, Shafer JA.; ''Regulation of formation of factor XIIIa by its fibrin substrates.''; PubMedEurope PMCScholia
Weitz JI, Hudoba M, Massel D, Maraganore J, Hirsh J.; ''Clot-bound thrombin is protected from inhibition by heparin-antithrombin III but is susceptible to inactivation by antithrombin III-independent inhibitors.''; PubMedEurope PMCScholia
Pan S, Iannotti MJ, Sifers RN.; ''Analysis of serpin secretion, misfolding, and surveillance in the endoplasmic reticulum.''; PubMedEurope PMCScholia
Yegneswaran S, Smirnov MD, Safa O, Esmon NL, Esmon CT, Johnson AE.; ''Relocating the active site of activated protein C eliminates the need for its protein S cofactor. A fluorescence resonance energy transfer study.''; PubMedEurope PMCScholia
Pipe SW, Eickhorst AN, McKinley SH, Saenko EL, Kaufman RJ.; ''Mild hemophilia A caused by increased rate of factor VIII A2 subunit dissociation: evidence for nonproteolytic inactivation of factor VIIIa in vivo.''; PubMedEurope PMCScholia
Rosing J, Hoekema L, Nicolaes GA, Thomassen MC, Hemker HC, Varadi K, Schwarz HP, Tans G.; ''Effects of protein S and factor Xa on peptide bond cleavages during inactivation of factor Va and factor VaR506Q by activated protein C.''; PubMedEurope PMCScholia
Di Scipio RG, Hermodson MA, Davie EW.; ''Activation of human factor X (Stuart factor) by a protease from Russell's viper venom.''; PubMedEurope PMCScholia
Hoeben RC, Fallaux FJ, Cramer SJ, van den Wollenberg DJ, van Ormondt H, Briët E, van der Eb AJ.; ''Expression of the blood-clotting factor-VIII cDNA is repressed by a transcriptional silencer located in its coding region.''; PubMedEurope PMCScholia
Gilbert GE, Furie BC, Furie B.; ''Binding of human factor VIII to phospholipid vesicles.''; PubMedEurope PMCScholia
Schmaier AH.; ''The physiologic basis of assembly and activation of the plasma kallikrein/kinin system.''; PubMedEurope PMCScholia
Kellermann J, Lottspeich F, Henschen A, Müller-Esterl W.; ''Completion of the primary structure of human high-molecular-mass kininogen. The amino acid sequence of the entire heavy chain and evidence for its evolution by gene triplication.''; PubMedEurope PMCScholia
Wienen W, Stassen JM, Priepke H, Ries UJ, Hauel N.; ''In-vitro profile and ex-vivo anticoagulant activity of the direct thrombin inhibitor dabigatran and its orally active prodrug, dabigatran etexilate.''; PubMedEurope PMCScholia
Butkowski RJ, Elion J, Downing MR, Mann KG.; ''Primary structure of human prethrombin 2 and alpha-thrombin.''; PubMedEurope PMCScholia
Greengard JS, Heeb MJ, Ersdal E, Walsh PN, Griffin JH.; ''Binding of coagulation factor XI to washed human platelets.''; PubMedEurope PMCScholia
Holmer E, Söderberg K, Bergqvist D, Lindahl U.; ''Heparin and its low molecular weight derivatives: anticoagulant and antithrombotic properties.''; PubMedEurope PMCScholia
Kurosawa S, Esmon CT, Stearns-Kurosawa DJ.; ''The soluble endothelial protein C receptor binds to activated neutrophils: involvement of proteinase-3 and CD11b/CD18.''; PubMedEurope PMCScholia
Kurachi K, Kurachi S, Furukawa M, Yao SN.; ''Biology of factor IX.''; PubMedEurope PMCScholia
Fibrinogen is a hexamer, containing two fibrinogen alpha chains, two fibrinogen beta chains, and two fibrinogen gamma chains, held together by disulfide bonds.
Fibrin is a hexamer of two fibrinogen alpha chains, two fibrinogen beta chains, and two fibrinogen gamma chains, held together by disulfide bonds. It is formed in vivo by the thrombin-catalyzed removal of amino terminal fibinopeptides from the A alpha and B beta chains of fibrinogen. This fibrin hexamer ("fibrin monomer") is the subunit that multimerizes to form a fibrin clot ("fibrin multimer").
The fibrin "monomers" formed by the action of thrombin on fibrinogen associate spontaneously into multimers. This association can follow several distinct pathways and may be able to form several types of higher-order structures. All of these possibilities are represented in Reactome as a fibrin trimer.
Activated thrombin cleaves the A chains of factor XIII tetramers in a reaction stimulated by the presence of fibrin multimers (Lewis et al. 1985). The amino terminal portions of the A chains are released as activation peptides, which have no known function. The resulting factor XIII tetramer remains catalytically inactive.
The membrane-bound Va:Xa (prothrombinase) complex rapidly activates large amounts of thrombin. Factor Xa (aka Factor X heavy chain), a cleavage product of coagulation factor X (F10), is a vitamin K-dependent glycoprotein able to convert prothrombin to thrombin during the blood clotting process (Mann et al. 1988, Orfeo et al. 2004). Factor Xa is a target for direct oral anticoagulant (DOAC) drugs that are direct factor Xa inhibitors (the so-called 'xabans') and used in the treatment and prevention of thromboembolic disorders (Galanis et al. 2014).
Factors Va and Xa associate on a membrane surface to form a complex in which the activity of factor Xa on prothrombin is greatly increased (Mann et al. 1988). The presence of negatively charged phospholipid in the membrane greatly facilitates this process, a feature that may contribute to its localization, as such phospholipids are normally on the cytosolic face of the plasma membrane (Devaux 1992), but could be exposed to the extracellular space following platelet activation or mechanical injury to endothelial cells.
Activated thrombin (factor IIa) catalyzes the conversion of factor V to factor Va (activated factor V). The activation peptide released in this reaction has no known function.
Membrane-bound factor Xa catalyzes the activation of small amounts of thrombin. The amino terminal portion of prothrombin is released as an activation peptide, which can be cleaved further by activated thrombin. Neither the full-length activation peptide nor its cleavage products have known functions.
Factor Xa (aka Factor X heavy chain), a cleavage product of coagulation factor X (F10), is a vitamin K-dependent glycoprotein able to convert prothrombin to thrombin during the blood clotting process. Factor Xa is a target for direct oral anticoagulant (DOAC) drugs that are direct factor Xa inhibitors (the so-called 'xabans') and used in the treatment and prevention of thromboembolic disorders (Galanis et al. 2014).
Factor VIIa, bound to tissue factor at the endothelial cell surface (the "extrinsic tenase complex"), catalyzes the formation of activated factor X with high efficiency. The amino terminal part of the heavy chain of factor X, the factor X activation peptide, is released. (This peptide has no known function.)
Factor VII, bound to tissue factor at the endothelial cell surface, catalyzes the activation of factor X from plasma with moderate efficiency. The amino terminal part of the heavy chain of factor X, the factor X activation peptide, is released. (This peptide has no known function.)
Antithrombin III binds to membrane-associated heparin, e.g., on the surface of a normal endothelial cell. This binding event increases the affinity of antithrombin III for thrombin approximately 1000-fold.
Factor VIIa, bound to tissue factor at the endothelial cell surface, catalyzes the formation of activated factor IX with high efficiency. The amino terminal part of the heavy chain of factor IX, the factor IX activation peptide, is released. (This peptide has no known function.)
TFPI binds to the factor VIIa:TF complex and to factor Xa at the endothelial surface, forming a stable heterotetrameric complex in which factor VIIa is catalytically inactive.
The alpha and beta chains of fibrinogen hexamer are cleaved by thrombin to generate fibrin monomer (Ni et al. 1989). The amino terminal regions of the cleaved alpha and beta chains are released (fibrinopeptides A and B respectively).
Fibrin monomers rapidly and spontaneously associate into large multimers, binding to one another via sites created by fibrinopeptide release (Laudano and Doolittelle 1980). The process of multimerization, and the range of multimer structures that can form in vivo and in vitro, have been studied in detail (Doolittle 1984). Here, multimer size has arbitrarily been set to three fibrin monomers.
Once the A chains of the Factor XIII tetramer have been cleaved by thrombin, the complex dissociates and the resulting A chain dimer binds Ca++ (one per peptide monomer) to form activated factor XIII (factor XIIIa).
Fibrin multimers are stabilized by the formation of multiple covalent crosslinks between the side chains of specific lysine and glutamine residues in fibrinogen alpha and gamma chains, catalyzed by factor XIIIa.
Antithrombin III in the complex is cleaved by thrombin, thereupon undergoing a conformational change that stabilizes the thrombin:antithrombin III complex, trapping and inactivating the thrombin moiety.
The same conformational change that traps thrombin in its complex with cleaved antithrombin III also decreases the affinity of the latter for heparin, and the complex of cleaved antithrombin III and thrombin dissociates from the cell-bound heparin molecule.
Activated protein C cleaves peptide bonds in activated factor V (factor Va), converting it to an inactive form (factor Vi). APC proteolysis involves cleavage of the factor Va heavy chain at Arg-334 (306 if signal peptide is not included) and Arg-534 (506 with no signal peptide) (Nicolaes et al. 1985). Most factor Va molecules are initially cleaved at Arg-534, yielding a partially active intermediate, followed by complete inactivation through cleavage at Arg-334 (Kalafatis et al. 1994). Factor Xa inhibits Arg-534 cleavage but this effect is mitigated by Protein S (Norstrom et al. 2006). A mutation of the APC cleavage sites in Fv at Arg-534Gln a.k.a. FVLeiden is the most common identifiable hereditary risk factor for venous thrombosis among Caucasians (Camire 2011).
Thrombin complexed with thrombomodulin at the endothelial cell surface cleaves the heavy chain of protein C, generating activated protein C and an activation peptide. The activation peptide has no known function.
Activated thrombin (factor IIa) binds to thrombomodulin at the external face of the plasma membrane, forming a thrombin:thrombomodulin complex. In this complexed form, the activity of thrombin towards protein C is greatly increased, and as thrombomodulin is particularly abundant on the surfaces of endothelial cells, this association plays a major role in restricting clot formation.
Factor VIII binds to von Willebrand factor to form a complex. This complex stabilizes factor VIII, which otherwise has a very short half-life in the blood.
Factor VIII (Vehar et al. 1984) is a heterodimer containing a heavy and a light polypeptide chain, generated by the proteolytic cleavage of a single large precursor polypeptide. Several forms of the heavy chain are found in vivo, all functionally the same but differing in the amount of the B domain removed by proteolysis. The single form annotated here is the shortest one (Eaton et al. 1986; Hill-Eubanks et al. 1989).
In vitro, von Willebrand factor (Titani et al. 1986) can form complexes with factor VIII with a 1:1 stoichiometry. The complexes that form in vivo, however, involve large multimers of von Willebrand factor and varied, but always low, proportions of factor VIII (Vlot et al. 1995). A stoichiometry of one molecule of factor VIII associated with 50 of von Willebrand factor is typical in vivo, and is used here to annotate the factor VIII:von Willebrand factor complex.
Factor VIII complexed to von Willibrand factor in the blood is cleaved into several smaller polypeptides that remain associated. The acidic polypeptide on the aminoterminal side of the A3 domain of the light chain is released, however, and as this polypeptide mediates the association of factor VIII with von Willibrand factor, the activated factor VIII is released. While several proteases are capable of catalyzing these cleavages in vitro, only thrombin is active on factor VIII:von Willibrand factor complexes under physiological conditions (Eaton et al. 1986; Hill-Eubanks et al. 1989; Lollar et al. 1988; Pieters et al. 1989).
Plasma factor XI binds to the platelet glycoprotein Ib:IX:V complex (Baglia et al. 2002; Greengard et al. 1986). In the body, this reaction occurs specifically on the surfaces of activated platelets, but not on endothelial cells (Baird and Walsh 2002). The stoichiometry of the platelet glycoprotein Ib:IX:V complex has not been established directly, but is inferred from the relative abundances of its components in platelet membranes (Modderman et al. 1992; Shrimpton et al. 2002).
Factor IXa, in a complex with factor VIIIa on the surfaces of activated platelets (the "intrinsic tenase complex"), catalyzes the formation of activated factor X with high efficiency. The amino terminal part of the heavy chain of factor X, the factor X activation peptide, is released. (This peptide has no known function.)
Prekallikrein (PK) associates specifically with kininogen (HK) on cell surfaces. In vivo, this reaction may occur primarily on the surfaces of endothelial cells in response to platelet activation (Lin et al. 1997; Motta et al. 1998; Mahdi et al. 2003).
Prekallikrein in a complex with kininogen and C1q binding protein on the plasma membrane is cleaved to generate active kallikrein, which remains bound to the complex. In the body, this reaction appears to occur on the surfaces of endothelial cells and may require the presence of activated platelets. Recent work indicates that the protease that cleaves prekallikrein under these conditions is prolylcarboxypeptidase. Although this enzyme was originally isolated from lysosomes (Odya et al. 1978; Tan et al. 1993), it is associated with plasma membranes of cultured human endothelial cells in vitro (Moreira et al. 2002; Shariat-Madar et al. 2002), and the purified recombinant enzyme efficiently cleaves prekallikrein (Shariat-Madar et al. 2004). In contrast factor XII, despite its activity on prekallikrein in vitro, appears not to be responsible for prekallikrein activation on the cell surface (Rojkjaer et al. 1998).
Factors VIIIa and IXa associate on cell surfaces to form a complex that very efficiently catalyzes the activation of factor X, the so-called "intrinsic tenase complex". In vitro, negatively charged phospholipids can provide an appropriate surface. In the body, the surface is provided by the plasma membranes of activated platelets (Gilbert and Arena 1996).
Factor XI, bound to the cell surface, is converted to activated factor XI (factor XIa). Chemically, this reaction involves the cleavage of a single peptide bond in each subunit of the factor XI homodimer; intra- and inter-chain disulfide bonds hold the resulting four polypeptides together (Bouma and Griffin 1977; Kurachi and Davie 1977; McMullen et al. 1991). In the body, this reaction occurs on the surfaces of activated platelets (Greengard et al. 1986; Baglia et al. 2002; Baird and Walsh 2002); when this reaction occurs as a step in the intrinsic ("contact") pathway of blood coagulation, it is catalyzed by activated factor XIIa (Kurachi and Davie 1977, Baglia and Walsh 2000) which in turn is generated through the interactions of factor XII, kallikrein, and kininogen on endothelial cell surfaces (Schmaier 2004).
The cleavage of kininogen (HK, high molecular weight kininogen) yields activated kininogen and the vasoactive peptide bradykinin (Kerbirou and Griffin 1979; Lottspeich et al. 1985; Kellerman et al. 1986). In vivo, this reaction is catalyzed by activated kallikrein, takes places within the kallikrein:kininogen:C1q binding protein tetramer complex on the endothelial cell surface, and results in the release of kallikrein and bradykinin (Motta et al. 1998).
Cleavage of a single peptide bond converts factor XII to activated factor XII (factor XIIa) (Fujikawa and McMullen 1983; McMullen and Fujikawa 1985). Identification of the catalytic activity or activities responsible for this cleavage has not been straightforward. Studies in vitro have demonstrated the autoactivation of factor XII as well as activation by kallikrein. Both reactions require the presence of negatively charged surfaces and are accelerated in the presence of kininogen (high molecular weight kininogen, HK) (Griffin and Cochrane 1976; Meier et al. 1977; Silverberg et al. 1980). Recent work suggests that factor XII activation in vivo may occur primarily on endothelial cell surfaces and that, as in vitro, association with kininogen may accelerate the reaction (Mahdi et al. 2002; Schmaier 2004), although alternative pathways and alternative mechanisms for associating factor XII with the cell surface have not been excluded (Joseph et al. 2001).
Factor XIa, bound to platelet glycoprotein (GP) Ib:IX:V on the platelet cell surface, catalyzes the formation of activated factor IX with high efficiency in a reaction that requires Ca++. The amino terminal part of the heavy chain of factor IX, the factor IX activation peptide, is released. (This peptide has no known function.)
Activated kallikrein binds to alpha2-macroglobulin (Sottrup-Jensen et al. 1984), forming a stable and enzymatically inactive complex. Under normal conditions in vivo, this reaction appears to be responsible for the inactivation of about 1/6 of activated kallikrein (with C1Inh responsible for the inactivation of about 5/6) (Harpel et al. 1985).
Kininogen (high molecular weight kininogen; HK) associates with C1q binding protein on the cell surface in a reaction dependent on Zn++ (Joseph et al. 1996). In the body, the Zn++ needed to drive this reaction may be provided locally by Zn++ release from activated platelets (Mahdi et al. 2002). The C1q binding protein is inferred to form tetramers based on the properties of purified recombinant protein in vitro (Ghebrehiwet et al. 1994); the stoichiometry of the cell surface complex has not been determined directly.
Activated factor XII (factor XIIa) binds to C1Inh (C1 inhibitor - Bock et al. 1986) to form a stable, inactive complex (Schneider et al. 1973). While several protease inhibitors can form stable complexes with XIIa in vitro, only C1Inh does so to a significant extent under normal conditions in vivo (Pixley et al. 1985).
Activated kallikrein binds to C1Inh (plasma protease C1 inhibitor) (Bock et al. 1986), forming a stable and enzymatically inactive complex. This reaction appears to be the major means by which kallikrein is inactivated (kallikrein can also be inactivated by binding to alpha2-macroglobulin) (Harpel et al. 1985; Ratnoff et al. 1969).
Factor XI, bound to the cell surface, is converted to activated factor XI (factor XIa). In the body, this reaction occurs on the surfaces of activated platelets (Baglia et al. 2002). Small quantities of factor XI can be activated in a reaction catalyzed by factor XIIa, to initiate formation of a fibrin clot. However, the efficient activation of larger quantities of factor XI, needed to propagate the blood clotting process, appears to be mediated by thrombin (Baglia and Walsh 2000; Gailani and Broze 1993; Naito and Fujikawa 1991; Oliver et al. 1999; Monroe et al. 2002).
SERPIND1 (Heparin cofactor 2) is a serine endopeptidase inhibitor (SERPIN) that acts as a pseudosubstrate for activated thrombin, forming a stable complex which has the effect of inactivating thrombin protease activity (Church et al. 1985), although with slower kinetics than SERPINC1 (antithrombin-III). The presence of the glycosaminoglycans heparin or dermatan sulphate increases thrombin inactivation 1000-fold (Van Deerlin & Tollefsen 199) by facilitating the interaction between the active site of thrombin and the reactive site of SERPIND1. Thrombin specificity is conferred by a 90-residue N-terminal extension that contains two acidic motifs containing sulphated Tyr residues, resembling the C-terminus of hirudin (Tollefsen et al. 1997). SERPIND1 also inhibits chymotrypsin and neutrophil cathepsin G, but in a glycosaminoglycan independent manner (Church et al. 1985). In contrast to SERPINC1 deficiency, SERPIND1 deficiency is not associated with venous thrombosis (Corral et al. 2004).
Protein C is best known for its anticoagulant activity, the proteolytic inactivation of FVa and FVIIIa on negatively charged phospholipid membranes. This is enhanced by cofactors protein S and FV (Rosing et al. 1995, Norstrom et al. 2006). Inactivation of FVa involves APC-mediated cleavages at Arg306 and Arg506. The rapid cleavage at Arg506 is kinetically favored over cleavage at Arg306, but results only in partial inactivation of FVa, whereas the slower cleavage at Arg306 results in a complete loss of FVa function (Kalafatis et al. 1994, Nicolaes et al. 1995). Protein S accelerates factor Va inactivation by selectively promoting the slow cleavage at Arg306 (Rosing et al. 1995). A mutation of the APC cleavage sites in FV Arg506Gln a.k.a. FVLeiden is the most common identifiable hereditary risk factor for venous thrombosis among Caucasians (Camire 2011). APC also has a role in the inactivation of FVIIIa (Regan et al. 1994). Similar to FVa inactivation, FVIIIa is cleaved by APC at Arg336 in the A1 subunit and at Arg562 in the A2 subunit, with either resulting in a complete loss of cofactor activity (O'Brien et al. 2000, Manithody et al. 2003). Both protein S and FV but not FVa enhance inactivation of FVIIIa by APC (O'Brien et al. 2000,57). By acting on FVa and FVIIIa Protein C down-regulates both primary and secondary thrombin formation, delaying clot formation and diminishing activation of TAFI, enhanced susceptibility of the clot to fibrinolysis, respectively. The latter effects of APC on secondary thrombin formation is sometimes referred to as APC’s profibrinolytic effect (Bajzar et al. 1996).
Physiological activation of protein C on the endothelial cell surface requires the binding of protein C to the endothelial protein C receptor PROCR (EPCR) as well as binding of thrombin to thrombomodulin (TM) (Stavenuiter et al. 2013). PROCR binding to protein C (Fukudome & Esmon 1994) augments by at least 5-fold the effect of thrombin-thrombomodulin on the rate of protein C activation (Stearns-Kurosawa et al. 1996, Taylor et al. 2001).
SERPINA5, also called Plasma serine protease inhibitor or Protein C inhibitor, inactivates serine proteases by binding irreversibly to their serine activation site. It is involved in the regulation of intravascular and extravascular proteolytic activities, promoting coagulation by inhibiting the anticoagulant complex Activated protein C (APC), but also acts as an anticoagulant factor by inhibiting blood coagulation factors such as prothrombin, factor XI, factor Xa, plasma kallikrein and fibrinolytic enzymes such as tissue- and urinary-type plasminogen activators. Its inhibitory activity is greatly enhanced in the presence of glycosaminoglycans (GAGs), heparin, thrombomodulin and phospholipids vesicles (Suzuki et al. 1985).
SERPINA5 inhibits activated protein C In the blood plasma and inhibits thromibin as part of the thrombin:thrombomodulin complex (Rezaie et al. 1995). On the other hand, PCI can also inhibit coagulation factors (Radtke et al. 2007). The SERPINA5:APC complex is a marker of thrombotic events (Kolbel et al. 2006), which suggests that despite low circulating SERPINA5 concentrations and rates of APC inhibition, its predominant role is procoagulatory (Li & Huntington 2008). This is due to the enhancing effect of GAGs, which line the vascular endothelium. Both SERPINA5 and APC bind to GAGs. The presence of heparin in vitro accelerates the maximal rate of inhibition by over 2000-fold (when accounting for dissociation constants) (Yang et al. 2002).
SERPINE2 (Protease nexin-1, PN1) is a specific and extremely efficient inhibitor of thrombin. Unlike other thrombin inhibitors belonging to the serpin family, SERPINE2 does not circulate in the blood (Bouton et al. 2012). Rather, it is bound to glycosaminoglycans on the surface of cell types including macrophages, smooth muscle cells and platelets, where it inhibits the signaling functions of thrombin. SERPINE2 sets the threshold for thrombin-induced platelet activation (Gronke et al. 1987, Boulaftali et al. 2010) and has been implicated in atherosclerosis (Bouton et al. 2012). Recent studies have demonstrated an important antithrombotic effect of platelet SERPINE2 in vitro and in vivo (Boulaftali et al. 2010).
Activated protein C (APC) can either dissociate from PROCR to exert its anticoagulant activity, or remain bound to PROCR where it influences multiple direct cellular activities. Dissociation of APC from PROCR allows APC to associate with other cell membrane surface molecules, various microparticles, or lipoproteins (e.g., high-density lipoprotein). As an anticoagulant, APC cleaves the activated cofactors Va (fVa) and VIIIa (fVIIIa), yielding inactivated cofactors, fVi and fVIIIi. This proteolytic inactivation is enhanced by protein cofactors (e.g., protein S, factor V) and lipids cofactors (e.g., phosphatidylserine, cardiolipin, glucosylceramide, or HDL).
Activated protein C binds to Protein S on appropriate cell surfaces where it inactivates factors Va and VIIIa. Protein S is best known as a cofactor for the Activated protein C (APC)-catalyzed inactivation of factor Va (Walker 1980). Protein S must be membrane-bound to display this cofactor activity (Hackeng et al. 1993). Protein S binding brings the active site of APC closer to the phospholipid cell surface (Yegneswaran et al. 1999).
APC proteolysis involves cleavage of the factor Va heavy chain at Arg-306 and Arg-506 (Nicolaes et al. 1985). Most factor Va molecules are initially cleaved at Arg506, yielding a partially active intermediate, followed by complete inactivation through cleavage at Arg306 (Kalafatis et al. 1994). Protein S stimulates the cleavage at Arg306 ~20-fold (Rosing et al. 1995) and also counteracts the protective effect of factor Xa on Arg506 cleavage (Norstrom et al. 2006).
Protein S also enhances the APC-mediated inactivation of factor VIIIa (van de Poel et al. 2001). Protein S and factor V act as synergistic cofactors in the APC-mediated inactivation of factor VIIIa (Shen & Dahlback 1994, Somajo et al. 2014).
A soluble form of PROCR (sEPCR) fully retains the ability to bind Protein C and Activated protein C (Kurosawa et al. 1997). This form increases up to 5-fold in patients with sepsis or systemic lupus erythematosus (Kurosawa et al. 1998), either from vascular injury or through a regulated proteolytic release of soluble receptor (Gu et al. 2000). sEPCR inhibits protein C activation over large vessel endothelium in culture, reflecting competition between the soluble and cell surface forms of PROCR (Liaw et al. 2000).
Activated Protein C (APC) is best known for its anticoagulant activity, the proteolytic inactivation of FVa and FVIIIa on negatively charged phospholipid membranes. This is enhanced by cofactors protein S and factor V (Rosing et al. 1995, Norstrom et al. 2006).
APC inactivates FVIIIa (Regan et al. 1994) with a mechanism similar to its inactivation of FVa. FVIIIa is cleaved by APC at Arg355 (336 if numbering excludes signal peptide) in the A1 subunit and at Arg581 (562 if numbering excludes signal peptide) in the A2 subunit (O'Brien et al. 2000, Manithody et al. 2003). The Arg355 cleavage is 6-fold faster than the Arg581 cleavage but does not fully inactivate factor VIIIa if dissociation of the A2 subunit is blocked (Gale et al. 2008). Protein S and Factor V (but not FVa) enhance the inactivation of FVIIIa by APC (O'Brien et al. 2000). Protein S and factor V both enhance cleavage at both sites, more so at Arg581 (Gale et al. 2008).
The A2 subunit of FVIIIa spontaneously dissociates, inactivating FVIIIa with a half-life of about 2 min (Fay et al. 1991).
By acting on FVa and FVIIIa Protein C down-regulates both primary and secondary thrombin formation, delaying clot formation and diminishing activation of TAFI, enhanced susceptibility of the clot to fibrinolysis, respectively. The latter effects of APC on secondary thrombin formation is sometimes referred to as APC’s profibrinolytic effect (Bajzar et al. 1996).
Soluble PROCR binds to activated neutrophils via PRTN3, also cknown as myeloblastin and (Leukocyte) proteinase-3 (Kurosawa et al. 2000). PRTN3 is the most abundant serine protease in neutrophils (Campbell et al. 2000). After neutrophil activation, PRTN3 is secreted from azurophil granules, rebinding to the neutrophil surface through an association with CD177 (NB1) a 60-kDa glycosyl-phosphatidylinositol (GPI)-linked cell surface glycoprotein, which is expressed on a subpopulation of neutrophils in 97% of healthy individuals (Knuckleburg et al. 2012). PRTN3 is partially protected from inactivation when associated with CD177 (Campbell et al. 2000) which may increase its efficacy. CD177 is a heterophilic binding partner for endothelial cell platelet-endothelial cell adhesion molecule (PECAM)-1, which is expressed at endothelial cell junctions where transmigration occurs (Sun et al. 2000) suggesting that CD177 directs at least a subpopulation of PRTN3 molecules to these areas to aid neutrophil diapedesis, perhaps through PRTN3 degradation of cell junction proteins or the extracellular matrix.
Membrane-bound thrombin-activated factor VIII (fVIIIa) functions as a cofactor for factor IXa in the factor Xase complex. Factors VIIIa and IXa associate with anionic phospholipid surfaces with high affinity (Respective Kd values ?1 nM and ~15nM, Gilbert et al. 1990, Mertens & Bertina 1984, Greengard et al. 1986). Studies using physiologic surfaces provide evidence for coordinated binding interactions of the enzyme, cofactor and substrate to discrete surface structures. For example, the presence of both (active site-modified) factor IXa and factor X increased both the number and the affinity of binding sites on activated platelets for factor VIIIa (Ahmad et al. 2000). However classical receptors for the constituents of factor Xase have not been identified (Fay 2004).
Cleavage of factor VIII light chain promotes a change in the conformation of the C2 domain that facilitates dissociation from VWF and enhances the affinity of factor VIIIa for anionic phospholipid surfaces (Saenko et al. 1998).
Membrane-bound thrombin-activated factor VIII (fVIIIa) functions as a cofactor for factor IXa in the factor Xase complex. Factors VIIIa and IXa associate with anionic phospholipid surfaces with high affinity (Respective Kd values ?1 nM and ~15nM, Gilbert et al. 1990, Mertens & Bertina 1984, Greengard et al. 1986). Studies using physiologic surfaces provide evidence for coordinated binding interactions of the enzyme, cofactor and substrate to discrete surface structures. For example, the presence of both (active site-modified) factor IXa and factor X increased both the number and the affinity of binding sites on activated platelets for factor VIIIa (Ahmad et al. 2000). However classical receptors for the constituents of factor Xase have not been identified (Fay 2004).
F2R (PAR1) mediates multiple cytoprotective effects of Activated proein C (APC) (Riewald et al. 2002, Griffin et al. 2007). In most, but not all, reported studies of APC’s beneficial effects on endothelial cells, the cellular receptors EPCR and F2R are required. These cytoprotective effects include anti-apoptotic activities, anti-inflammatory activities, protection of endothelial barrier functions, and favorable alteration of gene expression profiles. This paradigm in which EPCR-bound APC activates F2R to initiate signaling is consistent with many in vitro and in vivo data. Localization of APC signaling to caveolin-1-rich microdomains (caveolae) may help differentiate mechanisms for cytoprotective APC signaling versus proinflammatory thrombin signaling. Additional mechanisms for APC effects on cells may involve other receptors. These effects include APC anti-inflammatory effects on leukocytes or cytoprotective effects on dendritic cells and neurons. Other receptors may include F2RL2 (PAR3), various integrins e.g., Mac-1 (CD11b/CD18), Beta-1 integrins, Beta-3 integrins, S1P1, or the apolipoprotein E receptor 2 (LRP8) (Mosnier et al. 2007).
Factor Xa (aka Factor X heavy chain), a cleavage product of coagulation factor X (F10), is a vitamin K-dependent glycoprotein able to convert prothrombin to thrombin during the blood clotting process. Factor Xa is a target for direct oral anticoagulant (DOAC) drugs that are direct factor Xa inhibitors (the so-called 'xabans') which are used in the treatment and prevention of thromboembolic disorders (Galanis et al. 2014). Rivaroxaban (brand name Xarelto) was the first medically approved drug of this class (Abrams & Emerson 2009, Misselwitz et al. 2011). Rivaroxaban binds to and inhibits both free factor Xa and factor Xa bound in the prothrombinase complex (Roehrig et al. 2005). Other 'xabans' such as apixaban (Bhanwra & Ahluwalia 2014), edoxaban (Minor et al. 2015), eribaxaban (Bondarenko et al. 2013) and betrixaban (Zhang et al. 2009) share a similar mechanism of action to rivaroxaban (Nutescu et al. 2016).
Factor Xa (aka Factor X heavy chain), a cleavage product of coagulation factor X (F10), is a vitamin K-dependent glycoprotein able to convert prothrombin to thrombin during the blood clotting process. Factor Xa is a target for direct oral anticoagulant (DOAC) drugs that are direct factor Xa inhibitors (the so-called 'xabans') which are used in the treatment and prevention of thromboembolic disorders (Galanis et al. 2014, Nutescu et al. 2016). Rivaroxaban (brand name Xarelto) binds to and inhibits both free factor Xa and factor Xa bound in the prothrombinase complex (Va:Xa) (Roehrig et al. 2005). Rivaroxaban was the first medically approved drug of this class (Abrams & Emerson 2009, Misselwitz et al. 2011). Other 'xabans' such as apixaban (Bhanwra & Ahluwalia 2014), edoxaban (Minor et al. 2015), eribaxaban (Bondarenko et al. 2013) and betrixaban (Zhang et al. 2009) share a similar mechanism of action to rivaroxaban (Nutescu et al. 2016).
In the blood coagulation process, prothrombin is proteolytically cleaved to form thrombin (factor IIa) which in turn, acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin. Specifically, thrombin converts factor XI to XIa, factor VIII to VIIIa, factor V to Va, fibrinogen to fibrin, and factor XIII to XIIIa. The direct oral anticoagulant (DOAC) synthetic organic drugs dabigatran (brand name Pradaxa), argatroban (brand name Acova, Novastan; Exembol in the UK) and melagatran are potent, competitive direct thrombin inhibitors (DTIs). They reversibly and specifically binds both clot-bound and free thrombin (unlike warfarin or heparin), as well as inhibiting thrombin-induced platelet aggregation (Wienen et al. 2007, Stangier et al. 2007).
Commercially, dabigatran is formulated as a lipophilic prodrug, dabigatran etexilate, to promote gastrointestinal absorption before it is metabolised to the active drug. The kidneys excrete the majority (80%) of unchanged drug (Stangier et al. 2007). Argatroban is a synthetic inhibitor of thrombin derived from L-arginine, which has a relatively short period of binding only to thrombin’s active site (Hursting et al. 1997). It is given intravenously and is metabolised in the liver. Because of its hepatic metabolism, it may be used in patients with renal dysfunction. Melagatran is the active drug formed from the prodrug ximelagatran and is a competitive and rapid inhibitor of thrombin (Gustafsson et al. 1998). DuP 714 is a potent and specific thrombin inhibitor (Chiu et al. 1991).
A major downside of DOACs is that they don't have reversing antidotes if internal bleeding arises from their use. However, in the case of severe bleeding of patients on dabigatran, the antibody fragment idarucizumab reversed its anticoagulation effects of dabigatran within minutes (Pollack et al. 2015). This represents a novel anticoagulation reversing mechanism for a DOAC.
In the blood coagulation process, prothrombin is proteolytically cleaved to form thrombin (factor IIa) which in turn, acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin. Specifically, thrombin converts factor XI to XIa, factor VIII to VIIIa, factor V to Va, fibrinogen to fibrin, and factor XIII to XIIIa. Direct thrombin inhibitors (DTIs) represent a new class
of promising anticoagulation agents. DTIs are increasingly
being used instead of heparin to provide initial,
rapid anticoagulation. Unlike heparin, which requires a mediator (antithrombin) to potentiate anticoagulation, Peptide DTIs can inhibit free and bound thrombin directly. Lepirudin (brand name Refludan) is a recombinant hirudin derived from yeast cells (Weitz et al. 1990). Hirudin is a naturally occurring anticoagulant produced by the salivary glands of medicinal leeches. Bivalirudin (brand name Angiomax, Angiox) is a synthetic analog of hirudin, with a shorter period of binding to thrombin (Gladwell 2002). Desirudin (brand name Iprivask) is another recombinant hirudin derivative that directly inhibits free and fibrin-bound thrombin (Graetz et al. 2011).
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thrombin inactivating
complexesinhibitors
(compounds):IIainhibitors
(compounds)inhibitors
(peptide):IIainhibitors
(peptide)kininogen:C1q binding protein
tetramer(factor
IIa):SERPIND1XIa:GPIb:GPIX:GPV
complexWillebrand factor
multimerantithrombin
III:heparinAnnotated Interactions
thrombin inactivating
complexesthrombin inactivating
complexesthrombin inactivating
complexesthrombin inactivating
complexesthrombin inactivating
complexesinhibitors
(compounds):IIainhibitors
(compounds)inhibitors
(peptide):IIainhibitors
(peptide)Factor Xa (aka Factor X heavy chain), a cleavage product of coagulation factor X (F10), is a vitamin K-dependent glycoprotein able to convert prothrombin to thrombin during the blood clotting process. Factor Xa is a target for direct oral anticoagulant (DOAC) drugs that are direct factor Xa inhibitors (the so-called 'xabans') and used in the treatment and prevention of thromboembolic disorders (Galanis et al. 2014).
Factor VIII (Vehar et al. 1984) is a heterodimer containing a heavy and a light polypeptide chain, generated by the proteolytic cleavage of a single large precursor polypeptide. Several forms of the heavy chain are found in vivo, all functionally the same but differing in the amount of the B domain removed by proteolysis. The single form annotated here is the shortest one (Eaton et al. 1986; Hill-Eubanks et al. 1989).
In vitro, von Willebrand factor (Titani et al. 1986) can form complexes with factor VIII with a 1:1 stoichiometry. The complexes that form in vivo, however, involve large multimers of von Willebrand factor and varied, but always low, proportions of factor VIII (Vlot et al. 1995). A stoichiometry of one molecule of factor VIII associated with 50 of von Willebrand factor is typical in vivo, and is used here to annotate the factor VIII:von Willebrand factor complex.
SERPINA5 inhibits activated protein C In the blood plasma and inhibits thromibin as part of the thrombin:thrombomodulin complex (Rezaie et al. 1995). On the other hand, PCI can also inhibit coagulation factors (Radtke et al. 2007). The SERPINA5:APC complex is a marker of thrombotic events (Kolbel et al. 2006), which suggests that despite low circulating SERPINA5 concentrations and rates of APC inhibition, its predominant role is procoagulatory (Li & Huntington 2008). This is due to the enhancing effect of GAGs, which line the vascular endothelium. Both SERPINA5 and APC bind to GAGs. The presence of heparin in vitro accelerates the maximal rate of inhibition by over 2000-fold (when accounting for dissociation constants) (Yang et al. 2002).
Protein S is best known as a cofactor for the Activated protein C (APC)-catalyzed inactivation of factor Va (Walker 1980). Protein S must be membrane-bound to display this cofactor activity (Hackeng et al. 1993). Protein S binding brings the active site of APC closer to the phospholipid cell surface (Yegneswaran et al. 1999).
APC proteolysis involves cleavage of the factor Va heavy chain at Arg-306 and Arg-506 (Nicolaes et al. 1985). Most factor Va molecules are initially cleaved at Arg506, yielding a partially active intermediate, followed by complete inactivation through cleavage at Arg306 (Kalafatis et al. 1994). Protein S stimulates the cleavage at Arg306 ~20-fold (Rosing et al. 1995) and also counteracts the protective effect of factor Xa on Arg506 cleavage (Norstrom et al. 2006).
Protein S also enhances the APC-mediated inactivation of factor VIIIa (van de Poel et al. 2001). Protein S and factor V act as synergistic cofactors in the APC-mediated inactivation of factor VIIIa (Shen & Dahlback 1994, Somajo et al. 2014).
APC inactivates FVIIIa (Regan et al. 1994) with a mechanism similar to its inactivation of FVa. FVIIIa is cleaved by APC at Arg355 (336 if numbering excludes signal peptide) in the A1 subunit and at Arg581 (562 if numbering excludes signal peptide) in the A2 subunit (O'Brien et al. 2000, Manithody et al. 2003). The Arg355 cleavage is 6-fold faster than the Arg581 cleavage but does not fully inactivate factor VIIIa if dissociation of the A2 subunit is blocked (Gale et al. 2008). Protein S and Factor V (but not FVa) enhance the inactivation of FVIIIa by APC (O'Brien et al. 2000). Protein S and factor V both enhance cleavage at both sites, more so at Arg581 (Gale et al. 2008).
The A2 subunit of FVIIIa spontaneously dissociates, inactivating FVIIIa with a half-life of about 2 min (Fay et al. 1991).
By acting on FVa and FVIIIa Protein C down-regulates both primary and secondary thrombin formation, delaying clot formation and diminishing activation of TAFI, enhanced susceptibility of the clot to fibrinolysis, respectively. The latter effects of APC on secondary thrombin formation is sometimes referred to as APC’s profibrinolytic effect (Bajzar et al. 1996).
Membrane-bound thrombin-activated factor VIII (fVIIIa) functions as a cofactor for factor IXa in the factor Xase complex. Factors VIIIa and IXa associate with anionic phospholipid surfaces with high affinity (Respective Kd values ?1 nM and ~15nM, Gilbert et al. 1990, Mertens & Bertina 1984, Greengard et al. 1986). Studies using physiologic surfaces provide evidence for coordinated binding interactions of the enzyme, cofactor and substrate to discrete surface structures. For example, the presence of both (active site-modified) factor IXa and factor X increased both the number and the affinity of binding sites on activated platelets for factor VIIIa (Ahmad et al. 2000). However classical receptors for the constituents of factor Xase have not been identified (Fay 2004).
Commercially, dabigatran is formulated as a lipophilic prodrug, dabigatran etexilate, to promote gastrointestinal absorption before it is metabolised to the active drug. The kidneys excrete the majority (80%) of unchanged drug (Stangier et al. 2007). Argatroban is a synthetic inhibitor of thrombin derived from L-arginine, which has a relatively short period of binding only to thrombin’s active site (Hursting et al. 1997). It is given intravenously and is metabolised in the liver. Because of its hepatic metabolism, it may be used in patients with renal dysfunction. Melagatran is the active drug formed from the prodrug ximelagatran and is a competitive and rapid inhibitor of thrombin (Gustafsson et al. 1998). DuP 714 is a potent and specific thrombin inhibitor (Chiu et al. 1991).
A major downside of DOACs is that they don't have reversing antidotes if internal bleeding arises from their use. However, in the case of severe bleeding of patients on dabigatran, the antibody fragment idarucizumab reversed its anticoagulation effects of dabigatran within minutes (Pollack et al. 2015). This represents a novel anticoagulation reversing mechanism for a DOAC.
of promising anticoagulation agents. DTIs are increasingly being used instead of heparin to provide initial,
rapid anticoagulation. Unlike heparin, which requires a mediator (antithrombin) to potentiate anticoagulation, Peptide DTIs can inhibit free and bound thrombin directly. Lepirudin (brand name Refludan) is a recombinant hirudin derived from yeast cells (Weitz et al. 1990). Hirudin is a naturally occurring anticoagulant produced by the salivary glands of medicinal leeches. Bivalirudin (brand name Angiomax, Angiox) is a synthetic analog of hirudin, with a shorter period of binding to thrombin (Gladwell 2002). Desirudin (brand name Iprivask) is another recombinant hirudin derivative that directly inhibits free and fibrin-bound thrombin (Graetz et al. 2011).kininogen:C1q binding protein
tetramer(factor
IIa):SERPIND1XIa:GPIb:GPIX:GPV
complexXIa:GPIb:GPIX:GPV
complexXIa:GPIb:GPIX:GPV
complexWillebrand factor
multimerWillebrand factor
multimerantithrombin
III:heparinantithrombin
III:heparin