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Last Updated: 2019-08-16
Homocysteine is an amino acid and homologue of cysteine that appears in the body as a result of the degradation of methionine. In mammals, homocysteine is used to biosynthesize cysteine via the following pathway. First the enzyme cystathionine beta-synthetase irreversibly condenses homocysteine with L-serine, forming L-cystathionine. The L-cystathionine is then cleaved by cystathionine gamma-lyase, producing 2-oxobutanoate, L-cysteine, and ammonia. The 2-oxobutanoate is further broken down via the 2-oxobutanoate degradation pathway, producing citric acid cycle intermediates, while the L-cysteine goes to the cysteine metabolism pathway. The homocysteine degradation pathway composes a part of the larger methionine metabolism pathway.
Homocysteine Degradation References
Swaroop M, Bradley K, Ohura T, Tahara T, Roper MD, Rosenberg LE, Kraus JP: Rat cystathionine beta-synthase. Gene organization and alternative splicing. J Biol Chem. 1992 Jun 5;267(16):11455-61.Pubmed: 1597473
Ishihara S, Morohashi K, Sadano H, Kawabata S, Gotoh O, Omura T: Molecular cloning and sequence analysis of cDNA coding for rat liver hemoprotein H-450. J Biochem. 1990 Dec;108(6):899-902. doi: 10.1093/oxfordjournals.jbchem.a123310.Pubmed: 2089036
Abe K, Kimura H: The possible role of hydrogen sulfide as an endogenous neuromodulator. J Neurosci. 1996 Feb 1;16(3):1066-71.Pubmed: 8558235
Nishi N, Tanabe H, Oya H, Urushihara M, Miyanaka H, Wada F: Identification of probasin-related antigen as cystathionine gamma-lyase by molecular cloning. J Biol Chem. 1994 Jan 14;269(2):1015-9.Pubmed: 8288556
Erickson PF, Maxwell IH, Su LJ, Baumann M, Glode LM: Sequence of cDNA for rat cystathionine gamma-lyase and comparison of deduced amino acid sequence with related Escherichia coli enzymes. Biochem J. 1990 Jul 15;269(2):335-40. doi: 10.1042/bj2690335.Pubmed: 2201285
Lundby A, Secher A, Lage K, Nordsborg NB, Dmytriyev A, Lundby C, Olsen JV: Quantitative maps of protein phosphorylation sites across 14 different rat organs and tissues. Nat Commun. 2012 Jun 6;3:876. doi: 10.1038/ncomms1871.Pubmed: 22673903
This pathway was propagated using PathWhiz - Pon, A. et al. Pathways with PathWhiz (2015) Nucleic Acids Res. 43(Web Server issue): W552–W559.
Propagated from SMP0000455
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