Metabolism of cofactors (Homo sapiens)

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9353530, 32, 3742312, 3, 18, 26, 414, 172636374, 2911, 25, 4010, 12, 22, 237, 381519, 334367, 388, 164211, 4013, 24, 271420, 21542mitochondrial matrixcytosolendoplasmic reticulum lumenmitochondrial intermembrane spaceperoxisomal matrixBH4 H+CALM1 BH4 2GCHFR:GCH1Fe2+ O2IPPP2xPalmC-MyrG-p-S1177-NOS3 NADP+Q10H2isocitrate-oxoglutarate transporterAdoMetH+Fe2+GCH1 decamerNADP+FPPAdoMetH2Oheme Ca2+ e-Metabolism of nitricoxide: NOS3activation andregulationH2OPDSS1/2 tetramerZn2+ Fe3+NADP+NADPHNADP+PPip-T308,S473-AKT1 H+COQ3(?-369)NADP+DMPhOH monooxygenaseZn2+ SPR dimer2xPalmC-MyrG-p-S1177-NOS3 2OGPTPS hexamerAsc.-DHNTPHSP90AA1 p-S1177-eNOS:CaM:HSP90:p-AKT1:BH2DeMQ10H2BH4p-S1177-eNOS:CaM:HSP90:p-AKT1:BH4BH3.p-PTPS hexamerBH4 ADPAscH-heme p-S1177-eNOS:CaM:HSP90:p-AKT1MHDBDHFR dimer2OGFMN COQ3(?-369)NADPHGCH1 all-E-10PrP2PPiGCHFR GCHFR pentamerFAD DHFR NADPHNADPHATPZn2+ COQ2GTPsepiapterinO2Mg2+ PDSS1 GCHFR p-T308,S473-AKT1 PTHPCOQ5PDSS2 DHDBCO2NADP+PRKG2FMN MDMQ10H2H+AdoHcyCALM1 DMQ10H2PHBNADPH2xPalmC-MyrG-p-S1177-NOS3 NADP+p-SPR dimerH+p-S213-SPR H2OHCOOHCO2FAD AdoHcyIDH1 dimerheme CALM1 ISCIT2OGFMN NADPHL-PheMHDB decarboxylaseBH2SPR IDH1 COQ9 H+NADP+H2OIDH1 HSP90AA1 COQ7 FAD O2H+BH2 Zn2+ NADPHHSP90AA1 p-T308,S473-AKT1 COQ6:FADDHBPTS ATPFAD ADPH+H+AdoHcyPPPCOQ9 dimer:COQ7:Fe2+GCH1 Ca2+ CO2COQ6 p-S19-PTS PeroxynitriteCa2+ AdoMetDMPhOHISCITIDH1 dimer1, 34, 393828, 38


Description

Many proteins depend for their activity on cofactors, associated ions and small molecules. This module contains annotations of processes involved in the synthesis of cofactors, either de novo or from essential molecules consumed in the diet (vitamins), as well as regeneration of active forms of cofactors (Lipmann 1984). View original pathway at Reactome.

Comments

Reactome-Converter 
Pathway is converted from Reactome ID: 8978934
Reactome-version 
Reactome version: 73
Reactome Author 
Reactome Author: D'Eustachio, Peter

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Bibliography

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History

View all...
CompareRevisionActionTimeUserComment
114813view16:31, 25 January 2021ReactomeTeamReactome version 75
113258view11:32, 2 November 2020ReactomeTeamReactome version 74
112892view14:13, 16 October 2020DeSlOntology Term : 'tetrahydrobiopterin metabolic pathway' added !
112807view18:12, 9 October 2020DeSlOntology Term : 'metabolic pathway of cofactors, vitamins, nutrients' added !
112756view16:15, 9 October 2020ReactomeTeamNew pathway

External references

DataNodes

View all...
NameTypeDatabase referenceComment
2GCHFR:GCH1ComplexR-HSA-1474149 (Reactome)
2OGMetaboliteCHEBI:16810 (ChEBI)
2xPalmC-MyrG-p-S1177-NOS3 ProteinP29474 (Uniprot-TrEMBL)
ADPMetaboliteCHEBI:456216 (ChEBI)
ATPMetaboliteCHEBI:30616 (ChEBI)
AdoHcyMetaboliteCHEBI:16680 (ChEBI)
AdoMetMetaboliteCHEBI:15414 (ChEBI)
Asc.-MetaboliteCHEBI:59513 (ChEBI)
AscH-MetaboliteCHEBI:38290 (ChEBI)
BH2 MetaboliteCHEBI:15375 (ChEBI)
BH2MetaboliteCHEBI:15375 (ChEBI)
BH3.MetaboliteCHEBI:62772 (ChEBI)
BH4 MetaboliteCHEBI:15372 (ChEBI)
BH4MetaboliteCHEBI:15372 (ChEBI)
CALM1 ProteinP0DP23 (Uniprot-TrEMBL)
CO2MetaboliteCHEBI:16526 (ChEBI)
COQ2ProteinQ96H96 (Uniprot-TrEMBL)
COQ3(?-369)ProteinQ9NZJ6 (Uniprot-TrEMBL)
COQ5ProteinQ5HYK3 (Uniprot-TrEMBL)
COQ6 ProteinQ9Y2Z9 (Uniprot-TrEMBL)
COQ6:FADComplexR-HSA-2162308 (Reactome)
COQ7 ProteinQ99807 (Uniprot-TrEMBL)
COQ9 ProteinO75208 (Uniprot-TrEMBL)
COQ9 dimer:COQ7:Fe2+ComplexR-HSA-8933003 (Reactome)
Ca2+ MetaboliteCHEBI:29108 (ChEBI)
DHBMetaboliteCHEBI:64136 (ChEBI)
DHDBMetaboliteCHEBI:50775 (ChEBI)
DHFR ProteinP00374 (Uniprot-TrEMBL)
DHFR dimerComplexR-HSA-1497822 (Reactome)
DHNTPMetaboliteCHEBI:18372 (ChEBI)
DMPhOH monooxygenaseR-HSA-2167826 (Reactome)
DMPhOHMetaboliteCHEBI:50774 (ChEBI)
DMQ10H2MetaboliteCHEBI:64181 (ChEBI)
DeMQ10H2MetaboliteCHEBI:64182 (ChEBI)
FAD MetaboliteCHEBI:16238 (ChEBI)
FMN MetaboliteCHEBI:17621 (ChEBI)
FPPMetaboliteCHEBI:17407 (ChEBI)
Fe2+ MetaboliteCHEBI:29033 (ChEBI)
Fe2+MetaboliteCHEBI:29033 (ChEBI)
Fe3+MetaboliteCHEBI:29034 (ChEBI)
GCH1 ProteinP30793 (Uniprot-TrEMBL)
GCH1 decamerComplexR-HSA-1474144 (Reactome)
GCHFR ProteinP30047 (Uniprot-TrEMBL)
GCHFR pentamerComplexR-HSA-1474155 (Reactome)
GTPMetaboliteCHEBI:15996 (ChEBI)
H+MetaboliteCHEBI:15378 (ChEBI)
H2OMetaboliteCHEBI:15377 (ChEBI)
HCOOHMetaboliteCHEBI:30751 (ChEBI)
HSP90AA1 ProteinP07900 (Uniprot-TrEMBL)
IDH1 ProteinO75874 (Uniprot-TrEMBL)
IDH1 dimerComplexR-HSA-389557 (Reactome)
IDH1 dimerComplexR-HSA-389559 (Reactome)
IPPPMetaboliteCHEBI:16584 (ChEBI)
ISCITMetaboliteCHEBI:151 (ChEBI)
L-PheMetaboliteCHEBI:58095 (ChEBI)
MDMQ10H2MetaboliteCHEBI:64180 (ChEBI)
MHDB decarboxylaseR-HSA-2167848 (Reactome)
MHDBMetaboliteCHEBI:50776 (ChEBI)
Metabolism of nitric

oxide: NOS3 activation and

regulation
PathwayR-HSA-202131 (Reactome) Nitric oxide (NO), a multifunctional second messenger, is implicated in physiological processes in mammals that range from immune response and potentiation of synaptic transmission to dilation of blood vessels and muscle relaxation. NO is a highly active molecule that diffuses across cell membranes and cannot be stored inside the producing cell. Its signaling capacity is controlled at the levels of biosynthesis and local availability. Its production by NO synthases is under complex and tight control, being regulated at transcriptional and translational levels, through co- and posttranslational modifications, and by subcellular localization. NO is synthesized from L-arginine by a family of nitric oxide synthases (NOS). Three NOS isoforms have been characterized: neuronal NOS (nNOS, NOS1) primarily found in neuronal tissue and skeletal muscle; inducible NOS (iNOS, NOS2) originally isolated from macrophages and later discovered in many other cell types; and endothelial NOS (eNOS, NOS3) present in vascular endothelial cells, cardiac myocytes, and in blood platelets. The enzymatic activity of all three isoforms is dependent on calmodulin, which binds to nNOS and eNOS at elevated intracellular calcium levels, while it is tightly associated with iNOS even at basal calcium levels. As a result, the enzymatic activity of nNOS and eNOS is modulated by changes in intracellular calcium levels, leading to transient NO production, while iNOS continuously releases NO independent of fluctuations in intracellular calcium levels and is mainly regulated at the gene expression level (Pacher et al. 2007).

The NOS enzymes share a common basic structural organization and requirement for substrate cofactors for enzymatic activity. A central calmodulin-binding motif separates an NH2-terminal oxygenase domain from a COOH-terminal reductase domain. Binding sites for cofactors NADPH, FAD, and FMN are located within the reductase domain, while binding sites for tetrahydrobiopterin (BH4) and heme are located within the oxygenase domain. Once calmodulin binds, it facilitates electron transfer from the cofactors in the reductase domain to heme enabling nitric oxide production. Both nNOS and eNOS contain an additional insert (40-50 amino acids) in the middle of the FMN-binding subdomain that serves as autoinhibitory loop, destabilizing calmodulin binding at low calcium levels and inhibiting electron transfer from FMN to the heme in the absence of calmodulin. iNOS does not contain this insert.

In this Reactome pathway module, details of eNOS activation and regulation are annotated. Originally identified as endothelium-derived relaxing factor, eNOS derived NO is a critical signaling molecule in vascular homeostasis. It regulates blood pressure and vascular tone, and is involved in vascular smooth muscle cell proliferation, platelet aggregation, and leukocyte adhesion. Loss of endothelium derived NO is a key feature of endothelial dysfunction, implicated in the pathogenesis of hypertension and atherosclerosis. The endothelial isoform eNOS is unique among the nitric oxide synthase (NOS) family in that it is co-translationally modified at its amino terminus by myristoylation and is further acylated by palmitoylation (two residues next to the myristoylation site). These modifications target eNOS to the plasma membrane caveolae and lipid rafts.

Factors that stimulate eNOS activation and nitric oxide (NO) production include fluid shear stress generated by blood flow, vascular endothelial growth factor (VEGF), bradykinin, estrogen, insulin, and angiopoietin. The activity of eNOS is further regulated by numerous post-translational modifications, including protein-protein interactions, phosphorylation, and subcellular localization.

Following activation, eNOS shuttles between caveolae and other subcellular compartments such as the noncaveolar plasma membrane portions, Golgi apparatus, and perinuclear structures. This subcellular distribution is variable depending upon cell type and mode of activation.

Subcellular localization of eNOS has a profound effect on its ability to produce NO as the availability of its substrates and cofactors will vary with location. eNOS is primarily particulate, and depending on the cell type, eNOS can be found in several membrane compartments: plasma membrane caveolae, lipid rafts, and intracellular membranes such as the Golgi complex.

Mg2+ MetaboliteCHEBI:18420 (ChEBI)
NADP+MetaboliteCHEBI:18009 (ChEBI)
NADPHMetaboliteCHEBI:16474 (ChEBI)
O2MetaboliteCHEBI:15379 (ChEBI)
PDSS1 ProteinQ5T2R2 (Uniprot-TrEMBL)
PDSS1/2 tetramerComplexR-HSA-2162271 (Reactome)
PDSS2 ProteinQ86YH6 (Uniprot-TrEMBL)
PHBMetaboliteCHEBI:30763 (ChEBI)
PPPMetaboliteCHEBI:15266 (ChEBI)
PPiMetaboliteCHEBI:29888 (ChEBI)
PRKG2ProteinQ13237 (Uniprot-TrEMBL)
PTHPMetaboliteCHEBI:17804 (ChEBI)
PTPS hexamerComplexR-HSA-1497879 (Reactome)
PTS ProteinQ03393 (Uniprot-TrEMBL)
PeroxynitriteMetaboliteCHEBI:25941 (ChEBI)
Q10H2MetaboliteCHEBI:64183 (ChEBI)
SPR ProteinP35270 (Uniprot-TrEMBL)
SPR dimerComplexR-HSA-1497791 (Reactome)
Zn2+ MetaboliteCHEBI:29105 (ChEBI)
all-E-10PrP2MetaboliteCHEBI:61011 (ChEBI)
e-MetaboliteCHEBI:10545 (ChEBI)
heme MetaboliteCHEBI:17627 (ChEBI)
isocitrate-oxoglutarate transporterR-HSA-390344 (Reactome)
p-PTPS hexamerComplexR-HSA-1475058 (Reactome)
p-S1177-eNOS:CaM:HSP90:p-AKT1:BH2ComplexR-HSA-1497889 (Reactome)
p-S1177-eNOS:CaM:HSP90:p-AKT1:BH4ComplexR-HSA-1497830 (Reactome)
p-S1177-eNOS:CaM:HSP90:p-AKT1ComplexR-HSA-202121 (Reactome)
p-S19-PTS ProteinQ03393 (Uniprot-TrEMBL)
p-S213-SPR ProteinP35270 (Uniprot-TrEMBL)
p-SPR dimerComplexR-HSA-1497817 (Reactome)
p-T308,S473-AKT1 ProteinP31749 (Uniprot-TrEMBL)
sepiapterinMetaboliteCHEBI:16095 (ChEBI)

Annotated Interactions

View all...
SourceTargetTypeDatabase referenceComment
2GCHFR:GCH1ArrowR-HSA-1474158 (Reactome)
2GCHFR:GCH1TBarR-HSA-1474146 (Reactome)
2OGArrowR-HSA-389540 (Reactome)
2OGArrowR-HSA-389550 (Reactome)
2OGArrowR-HSA-390347 (Reactome)
2OGR-HSA-390347 (Reactome)
ADPArrowR-HSA-1475422 (Reactome)
ADPArrowR-HSA-1497853 (Reactome)
ATPR-HSA-1475422 (Reactome)
ATPR-HSA-1497853 (Reactome)
AdoHcyArrowR-HSA-2162186 (Reactome)
AdoHcyArrowR-HSA-2162188 (Reactome)
AdoHcyArrowR-HSA-2162193 (Reactome)
AdoMetR-HSA-2162186 (Reactome)
AdoMetR-HSA-2162188 (Reactome)
AdoMetR-HSA-2162193 (Reactome)
Asc.-ArrowR-HSA-1497855 (Reactome)
AscH-R-HSA-1497855 (Reactome)
BH2ArrowR-HSA-1497863 (Reactome)
BH2ArrowR-HSA-1497869 (Reactome)
BH2R-HSA-1497794 (Reactome)
BH2R-HSA-1497796 (Reactome)
BH3.ArrowR-HSA-1497824 (Reactome)
BH3.ArrowR-HSA-1497866 (Reactome)
BH3.R-HSA-1497855 (Reactome)
BH3.R-HSA-1497863 (Reactome)
BH3.R-HSA-1497883 (Reactome)
BH4ArrowR-HSA-1475414 (Reactome)
BH4ArrowR-HSA-1497794 (Reactome)
BH4ArrowR-HSA-1497796 (Reactome)
BH4ArrowR-HSA-1497855 (Reactome)
BH4ArrowR-HSA-1497883 (Reactome)
BH4R-HSA-1497784 (Reactome)
BH4R-HSA-1497824 (Reactome)
BH4R-HSA-1497866 (Reactome)
BH4TBarR-HSA-1474146 (Reactome)
CO2ArrowR-HSA-2162195 (Reactome)
CO2ArrowR-HSA-389540 (Reactome)
CO2ArrowR-HSA-389550 (Reactome)
COQ2mim-catalysisR-HSA-2162192 (Reactome)
COQ3(?-369)mim-catalysisR-HSA-2162186 (Reactome)
COQ3(?-369)mim-catalysisR-HSA-2162193 (Reactome)
COQ5mim-catalysisR-HSA-2162188 (Reactome)
COQ6:FADmim-catalysisR-HSA-2162187 (Reactome)
COQ9 dimer:COQ7:Fe2+mim-catalysisR-HSA-2162194 (Reactome)
DHBArrowR-HSA-2162192 (Reactome)
DHBR-HSA-2162187 (Reactome)
DHDBArrowR-HSA-2162187 (Reactome)
DHDBR-HSA-2162193 (Reactome)
DHFR dimermim-catalysisR-HSA-1497794 (Reactome)
DHNTPArrowR-HSA-1474146 (Reactome)
DHNTPR-HSA-1474184 (Reactome)
DMPhOH monooxygenasemim-catalysisR-HSA-2162191 (Reactome)
DMPhOHArrowR-HSA-2162195 (Reactome)
DMPhOHR-HSA-2162191 (Reactome)
DMQ10H2ArrowR-HSA-2162188 (Reactome)
DMQ10H2R-HSA-2162194 (Reactome)
DeMQ10H2ArrowR-HSA-2162194 (Reactome)
DeMQ10H2R-HSA-2162186 (Reactome)
FPPR-HSA-2162253 (Reactome)
Fe2+R-HSA-1497883 (Reactome)
Fe3+ArrowR-HSA-1497883 (Reactome)
GCH1 decamerR-HSA-1474158 (Reactome)
GCH1 decamermim-catalysisR-HSA-1474146 (Reactome)
GCHFR pentamerR-HSA-1474158 (Reactome)
GTPR-HSA-1474146 (Reactome)
H+ArrowR-HSA-2162186 (Reactome)
H+ArrowR-HSA-2162188 (Reactome)
H+ArrowR-HSA-2162193 (Reactome)
H+ArrowR-HSA-389540 (Reactome)
H+ArrowR-HSA-389550 (Reactome)
H+R-HSA-1497794 (Reactome)
H+R-HSA-1497869 (Reactome)
H+R-HSA-2162187 (Reactome)
H+R-HSA-2162191 (Reactome)
H+R-HSA-2162194 (Reactome)
H2OArrowR-HSA-2162187 (Reactome)
H2OArrowR-HSA-2162191 (Reactome)
H2OArrowR-HSA-2162194 (Reactome)
H2OR-HSA-1474146 (Reactome)
HCOOHArrowR-HSA-1474146 (Reactome)
IDH1 dimermim-catalysisR-HSA-389540 (Reactome)
IDH1 dimermim-catalysisR-HSA-389550 (Reactome)
IPPPR-HSA-2162253 (Reactome)
ISCITArrowR-HSA-390347 (Reactome)
ISCITR-HSA-389540 (Reactome)
ISCITR-HSA-389550 (Reactome)
ISCITR-HSA-390347 (Reactome)
L-PheArrowR-HSA-1474146 (Reactome)
MDMQ10H2ArrowR-HSA-2162191 (Reactome)
MDMQ10H2R-HSA-2162188 (Reactome)
MHDB decarboxylasemim-catalysisR-HSA-2162195 (Reactome)
MHDBArrowR-HSA-2162193 (Reactome)
MHDBR-HSA-2162195 (Reactome)
NADP+ArrowR-HSA-1475414 (Reactome)
NADP+ArrowR-HSA-1497794 (Reactome)
NADP+ArrowR-HSA-1497869 (Reactome)
NADP+ArrowR-HSA-2162187 (Reactome)
NADP+ArrowR-HSA-2162191 (Reactome)
NADP+ArrowR-HSA-2162194 (Reactome)
NADP+R-HSA-389540 (Reactome)
NADP+R-HSA-389550 (Reactome)
NADPHArrowR-HSA-389540 (Reactome)
NADPHArrowR-HSA-389550 (Reactome)
NADPHR-HSA-1475414 (Reactome)
NADPHR-HSA-1497794 (Reactome)
NADPHR-HSA-1497869 (Reactome)
NADPHR-HSA-2162187 (Reactome)
NADPHR-HSA-2162191 (Reactome)
NADPHR-HSA-2162194 (Reactome)
O2R-HSA-2162187 (Reactome)
O2R-HSA-2162191 (Reactome)
O2R-HSA-2162194 (Reactome)
PDSS1/2 tetramermim-catalysisR-HSA-2162253 (Reactome)
PHBR-HSA-2162192 (Reactome)
PPPArrowR-HSA-1474184 (Reactome)
PPiArrowR-HSA-2162192 (Reactome)
PPiArrowR-HSA-2162253 (Reactome)
PRKG2mim-catalysisR-HSA-1475422 (Reactome)
PRKG2mim-catalysisR-HSA-1497853 (Reactome)
PTHPArrowR-HSA-1474184 (Reactome)
PTHPR-HSA-1475414 (Reactome)
PTPS hexamerR-HSA-1475422 (Reactome)
PeroxynitriteR-HSA-1497866 (Reactome)
Q10H2ArrowR-HSA-2162186 (Reactome)
R-HSA-1474146 (Reactome) The first and rate-limiting enzyme in tetrahydrobiopterin de novo biosynthesis is GTP cyclohydrolase I (GCH1, GTPCHI). Three different isoforms are produced but only isoform 1 is functionally active (Gütlich et al. 1994). GCH1 is functional as a homodecamer. First, a monomer of GCH1 forms a dimer. Then five dimers arrange into a ring-like structure to form the homodecamer (Nar et al. 1995).
R-HSA-1474158 (Reactome) High levels of the end product, BH4, negatively regulates GCH1. It does this via GTP cyclohydrolase 1 feedback regulatory protein (GCHFR). BH4-dependant GCHFR in the form of a homopentamer complexes with the decameric GCH1 enzyme in the ratio 2:1 to inactivate it. L-phenylalanine reverses this inhibition. These regulatory steps control the biosynthesis of BH4. (Swick & Kapatos 2006, Chavan et al. 2006, Harada et al. 1993).
R-HSA-1474184 (Reactome) 6-pyruvoyl tetrahydrobiopterin synthase (PTPS) (Takikawa et al. 1986) catalyses the second step in BH4 biosynthesis, the dephosphorylation of DHNTP to 6-pyruvoyl-tetrahydropterin (PTHP). PTPS is believed to function as a homohexamer (Nar et al. 1994, Bürgisser et al. 1994) and has a requirement for Zn2+ (one Zn2+ ion bound per subunit) and Mg2+ ions for activity (Bürgisser et al. 1995). The phosphorylation of Ser-19 is an essential modification for enzyme activity (Scherer-Oppliger et al. 1999).
R-HSA-1475414 (Reactome) Sepiapterin reductase (SPR) (Ichinose et al. 1991) reduces DHNTP to tetrahydrobiopterin (BH4).
R-HSA-1475422 (Reactome) 6-pyruvoyl tetrahydrobiopterin synthase (PTPS) requires phosphorylation on Ser-19 for enzyme activity (Scherer-Oppliger et al. 1999).
R-HSA-1497784 (Reactome) The cofactor tetrahydrobiopterin (BH4) ensures endothelial nitric oxide synthase (eNOS) couples electron transfer to L-arginine oxidation (Berka et al. 2004). During catalysis, electrons derived from NADPH transfer to the flavins FAD and FMN in the reductase domain of eNOS and then on to the ferric heme in the oxygenase domain of eNOS. BH4 can donate an electron to intermediates in this electron transfer and is oxidised in the process, forming the BH3 radical. This radical can be reduced back to BH4 by iron, completing the cycle and forming ferrous iron again. Heme reduction enables O2 binding and L-arginine oxidation to occur within the oxygenase domain (Stuehr et al. 2009).
R-HSA-1497794 (Reactome) In the second salvage step, dihydrofolate reductase (DHFR) can regenerate BH4 from BH2, a process which increases the BH4:BH2 ratio providing BH4 for coupled eNOS production of NO. In mice cell lines, DHFR inhibition or knockdown diminishes the BH4:BH2 ratio and exacerbates eNOS uncoupling (Crabtree et al. 2009).
R-HSA-1497796 (Reactome) The oxidation product of BH4, 7,8-dihydrobiopterin (BH2), can compete with BH4 for binding to eNOS. This can lead to the uncoupling of eNOS and can result in the formation of reactive oxygen species (Vasquez-Vivar et al. 2002).
R-HSA-1497824 (Reactome) BH4 donates an electron to the eNOS catalytic cycle and is oxidised to the BH3 radical (BH3.-) (Berka et al. 2004).
R-HSA-1497853 (Reactome) To become active, sepiapterin reductase (SPR) must first be phosphorylated (serine 213 in humans) by Ca2+/calmodulin-dependent protein kinase II (Fujimoto et al. 2002, Katoh et al. 1994).
R-HSA-1497855 (Reactome) Ascorbate (AscH-) can reduce the BH3 radical back to BH4, thereby maintaining BH4 levels (Baker et al. 2001, Patel et al. 2002, Kuzkaya et al. 2003).
R-HSA-1497863 (Reactome) BH4 oxidation results in the radical BH3. which decays to 7,8-dihydrobiopterin (BH2) (Milstien & Katusic, 1999).
R-HSA-1497866 (Reactome) Peroxynitrite can oxidise BH4 to the BH3 radical, further reducing BH4 availability to couple eNOS activity and compounding the production of superoxide through uncoupled eNOS activity (Kuzkaya et al. 2003).
R-HSA-1497869 (Reactome) In the first of two salvage steps to maintain BH4 levels in the cell, sepiapterin is taken up by the cell and reduced by sepiapterin reductase (SRP) to form BH2 (Sawabe et al. 2008).
R-HSA-1497883 (Reactome) Heme iron from the oxygenase domain of eNOS can reduce the BH3 radical back to BH4, with itself being oxidised from the ferrous (Fe2+) back to the ferric (Fe3+) form (Berka et al. 2004).
R-HSA-2162186 (Reactome) Mitochondrial COQ3 is an O-methyltransferase required in the reaction to convert 3-demethylubiquinol-10 (DeMQ10H2) to ubiquinol-10 (Q10H2) (Jonassen & Clarke 2000).
R-HSA-2162187 (Reactome) A flavin-dependent monooxygenase involved in ubiquinone/ubiquinol biosynthesis, COQ6 (Heeringa et al. 2011) catalyses the C5-hydroxylation of 3-decaprenyl-4-hydroxybenzoic acid (DHB) to 3,4-dihydroxy-5-decaprenylbenzoic acid (DHDB). COQ6 is a peripheral membrane protein that localizes to the matrix side of the inner mitochondrial membrane (Gin et al. 2003). This reaction involving COQ6 is inferred from the equivalent reaction in yeast (Ozeir et al. 2011, Gin et al. 2003).
R-HSA-2162188 (Reactome) 2-methoxy-6-polyprenyl-1,4-benzoquinol methylase, mitochondrial (COQ5) catalyses the C-methyltransferase conversion of 2-methoxy-6-decaprenyl-1,4-benzoquinol (MDMQ10H2) to 6-methoxy-3-methyl-2-decaprenyl-1,4-benzoquinol (DMQ10H2). This reaction is inferred from the equivalent reaction in yeast (Barkovich et al. 1997).
R-HSA-2162191 (Reactome) 2-methoxy-6-decaprenylphenol (DMPhOH) is enzymatically converted to 2-methoxy-6-decaprenyl-1,4-benzoquinol (MDMQ10H2). It was thought at one time that the flavin-dependent monooxygenase, COQ6, was the enzyme that catalysed this reaction, however, it has been subsequently shown that COQ6 is not essential for this reaction (Ozeir et al. 2011). However, it is still believed that another member of the COQ family catalyses this event. This reaction is inferred from the equivalent reaction in yeast (Gin et al. 2003, Ozeir et al. 2011).
R-HSA-2162192 (Reactome) 4-hydroxybenzoate polyprenyltransferase, mitochondrial (COQ2) catalyses the combination of 4-hydroxybenzoic acid, aka para-hydroxybenzoic acid (PHB) with the polyisoprenoid tail all-trans-decaprenyl diphosphate (all-E-10PrP2) to form 3-decaprenyl-4-hydroxybenzoic acid (DHB) (Forsgren et a l. 2004, Tekle et al. 2008). This reaction is irreversible and occurs in the mitochondria.
R-HSA-2162193 (Reactome) Mitochondrial COQ3 is an O-methyltransferase required in the reaction to convert 3,4-dihydroxy-5-decaprenylbenzoic acid (DHDB) to 3-methoxy-4-hydroxy-5-decaprenylbenzoic acid (MHDB) (Jonassen & Clarke 2000).
R-HSA-2162194 (Reactome) Ubiquinone biosynthesis protein COQ7 homolog (COQ7) (Vajo et al. 1999) catalyses the hydroxylation of 6-methoxy-3-methyl-2-decaprenyl-1,4-benzoquinol (DMQ10H2) to 3-demethylubiquinol-10 (DeMQ10H2). This reaction is inferred from the equivalent reaction in yeast (Marbois & Clarke 1996, Tran et al. 2006). Mitochondrial ubiquinone biosynthesis protein COQ9 is a lipid-binding protein involved in the biosynthesis of coenzyme Q. It binds with COQ7, an interaction that may be necessary to present the lipid to COQ7 activity (Lohman et al. 2014).
R-HSA-2162195 (Reactome) 3-methoxy-4-hydroxy-5-decaprenylbenzoic acid (MHDB) is enzymatically decarboxylated to form 2-methoxy-6-decaprenylphenol (DMPhOH). At the present time the enzyme identity is unknown but is thought to be a member of the COQ family. This reaction is inferred from the equivalent reaction in yeast (Casey & Threlfall 1978, Goewert et al. 1981).
R-HSA-2162253 (Reactome) The polyprenyl diphosphate synthase consists of a tetramer comprising two units of decaprenyl-diphosphate synthase subunit 1 (PDSS1) and two units of decaprenyl-diphosphate synthase subunit 2 (PDSS2). It catalyses the combination of 2-trans,6-trans-farnesyl diphosphate (FPP) with isopentenyl diphosphate (IPPP) to form the polyisoprenoid tail all-trans-decaprenyl diphosphate (all-E-10PrP2) (Saiki et al. 2005, Tekle et al. 2008).
R-HSA-389540 (Reactome) Cytosolic IDH1 (isocitrate dehydrogenase 1) homodimer catalyzes the reaction of isocitrate and NADP+ to form 2-oxoglutarate, CO2, and NADPH + H+. The same enzyme can also localize to peroxisomes (Geisbrecht and Gould 1999; Xu et al. 2004).
R-HSA-389550 (Reactome) Peroxisomal IDH1 (isocitrate dehydrogenase 1) homodimer catalyzes the reaction of isocitrate and NADP+ to form 2-oxoglutarate, CO2, and NADPH + H+. The same enzyme can also localize to the cytosol in at least some cell types (Geisbrecht and Gould 1999; Xu et al. 2004).
R-HSA-390347 (Reactome) A specific transport process that exchanges 2-oxoglutarate for isocitrate across a lipid membrane has been reconstituted in vitro with proteins purified from bovine peroxisomal membranes. The specific protein or proteins that mediate this transport process have not yet been identified in any mammalian system, however (Visser et al. 2006).
SPR dimerR-HSA-1497853 (Reactome)
all-E-10PrP2ArrowR-HSA-2162253 (Reactome)
all-E-10PrP2R-HSA-2162192 (Reactome)
e-ArrowR-HSA-1497824 (Reactome)
isocitrate-oxoglutarate transportermim-catalysisR-HSA-390347 (Reactome)
p-PTPS hexamerArrowR-HSA-1475422 (Reactome)
p-PTPS hexamermim-catalysisR-HSA-1474184 (Reactome)
p-S1177-eNOS:CaM:HSP90:p-AKT1:BH2ArrowR-HSA-1497796 (Reactome)
p-S1177-eNOS:CaM:HSP90:p-AKT1:BH4ArrowR-HSA-1497784 (Reactome)
p-S1177-eNOS:CaM:HSP90:p-AKT1:BH4R-HSA-1497796 (Reactome)
p-S1177-eNOS:CaM:HSP90:p-AKT1R-HSA-1497784 (Reactome)
p-SPR dimerArrowR-HSA-1497853 (Reactome)
p-SPR dimermim-catalysisR-HSA-1475414 (Reactome)
p-SPR dimermim-catalysisR-HSA-1497869 (Reactome)
sepiapterinR-HSA-1497869 (Reactome)
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