Homocysteine and cysteine interconversion (Saccharomyces cerevisiae)

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Description

The metabolic interconversion of cysteine and homocysteine via formation of a cystathionine intermediate is known as the transsulfuration pathway. While the transsulfuration pathway proceeds in only one direction in many bacteria and fungi, S. cerevisiae encodes for both a forward and reverse version of the pathway and is able to convert cysteine and homocysteine to one or the other reversibly. In the forward pathway, cysteine reacts with O-acetylhomoserine in a reaction catalyzed by cystathionine -synthase to form cystathionine. Cystathionine is then cleaved by cystathionine -lyase, yielding pyruvate, ammonia, and homocysteine. In S. cerevisiae, cystathionine -synthase and -lyase are thought to be encoded by STR2 and STR3 respectively, due to their similarity to the aforementioned enzymes in other organisms and the inability of str2 or str3 null mutants to utilize cysteine as a sole sulfur source. In the reverse pathway, cystathionine -synthase (Cys4p) catalyzes the condensation of homocysteine and serine to form cystathionine. Cystathionine -lyase (Cys3p) then catalyzes hydrolysis of cystathionine to produce cysteine, -ketobutyrate, and ammonia.

The presence of two transsulfuration pathways in S. cerevisiae enables the cell to acquire methionine from cysteine and vice-versa by using homocysteine as an intermediate. Homocysteine derived from cysteine in the forward transsulfuration pathway can be converted to methionine, while homocysteine derived from methionine can be converted to cysteine via the reverse transsulfuration pathway. This enables S. cerevisiae to utilize methionine or cysteine as a sole source of sulfur.

Source: https://pathway.yeastgenome.org/

Comments

 
Based on http://pathway.yeastgenome.org/biocyc/

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Ontology Terms

 

Bibliography

  1. Thomas D, Surdin-Kerjan Y; ''Metabolism of sulfur amino acids in Saccharomyces cerevisiae.''; Microbiol Mol Biol Rev, 1997 PubMed Europe PMC Scholia
  2. ''homocysteine and cysteine interconversion''; YeastPathways,

History

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CompareRevisionActionTimeUserComment
135654view01:11, 18 October 2024KhanspersOntology Term : 'classic metabolic pathway' added !
135653view01:11, 18 October 2024Khanspersupdated reference
135652view01:10, 18 October 2024Khanspersoverhaul
135641view05:10, 8 October 2024KhanspersModified description
117301view11:17, 20 May 2021EweitzModified title
92820view19:35, 8 July 2017AlexanderPicoRemoved old genmapp tags and unused attributes
92819view19:35, 8 July 2017AlexanderPicoReverted to version '03:47, 11 July 2013' by AlexanderPico
92791view15:18, 6 July 2017DeSlQuick edit to datanode annotation or property
69755view10:47, 11 July 2013EgonwMarked a few DataNodes with CAS registry numbers as metabolites.
69642view20:37, 8 July 2013MaintBotUpdated to 2013 gpml schema
67340view10:39, 26 June 2013Christine ChichesterOntology Term : 'cysteine metabolic pathway' added !
41880view04:52, 2 March 2011MaintBotRemoved redundant pathway information and comments
36653view22:39, 9 April 2010MaintBotDescription and bibliography added from SGD
20951view11:30, 14 November 2008MaintBot[[Pathway:Saccharomyces cerevisiae:Homocysteine and Cysteine Interconversion]] moved to [[Pathway:WP128]]: Moved to stable identifier
12750view08:01, 17 May 2008MaintBotautomated metabolite conversion
8786view14:09, 7 January 2008MaintBotAdded to category $category
8784view14:09, 7 January 2008M.BraymerUploaded new pathway

External references

DataNodes

View all...
NameTypeDatabase referenceComment
2-oxobutanoateMetabolite16763 (ChEBI)
CYS3GeneProductS000000010 (SGD)
CYS4GeneProductS000003387 (SGD)
H2OMetabolite15377 (ChEBI)
L-cysteineMetabolite52-90-4 (CAS)
L-serineMetabolite56-45-1 (CAS)
NH3Metabolite16134 (ChEBI)
O-acetyl-L-homoserineMetabolite57716 (ChEBI)
STR2GeneProductS000003891 (SGD)
STR3GeneProductS000003152 (SGD)
acetateMetabolite64-19-7 (CAS)
cystathionineMetabolite56-88-2 (CAS)
homocysteineMetabolite6027-13-0 (CAS)
pyruvateMetabolite15361 (ChEBI)

Annotated Interactions

No annotated interactions
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