The Enzyme Database

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Accepted name: cysteine-S-conjugate β-lyase
Reaction: an L-cysteine-S-conjugate + H2O = a thiol + NH3 + pyruvate (overall reaction)
(1a) an L-cysteine-S-conjugate = a thiol + 2-aminoprop-2-enoate
(1b) 2-aminoprop-2-enoate = 2-iminopropanoate (spontaneous)
(1c) 2-iminopropanoate + H2O = pyruvate + NH3 (spontaneous)
Other name(s): cysteine conjugate β-lyase; glutamine transaminase K/cysteine conjugate β-lyase; L-cysteine-S-conjugate thiol-lyase (deaminating); cystathionine β-lyase; β-cystathionase; cystine lyase; cystathionine L-homocysteine-lyase (deaminating); L-cystathionine L-homocysteine-lyase (deaminating); CBL; S-alkylcysteine lyase; S-alkylcysteinase; alkylcysteine lyase; S-alkyl-L-cysteine lyase; S-alkyl-L-cysteinase; alkyl cysteine lyase; S-alkyl-L-cysteine alkylthiol-lyase (deaminating)
Systematic name: L-cysteine-S-conjugate thiol-lyase (deaminating; 2-aminoprop-2-enoate-forming)
Comments: A pyridoxal-phosphate protein. The enzyme is promiscuous regarding the moiety conjugated to L-cysteine, and can accept both aliphatic and aromatic substitutions. The enzyme cleaves a carbon-sulfur bond, releasing a thiol and an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form pyruvate and ammonia. While bacteria and plants have dedicated enzymes, all of the animal enzymes discovered thus far are bifunctional, most of which also act as aminotransferases.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 68652-57-3
1.  Flavin, M. and Slaughter, C. Cystathionine cleavage enzymes of Neurospora. J. Biol. Chem. 239 (1964) 2212–2219. [PMID: 14209950]
2.  Tateishi, M., Suzuki, S. and Shimizu, H. Cysteine conjugate β-lyase in rat liver. A novel enzyme catalyzing formation of thiol-containing metabolites of drugs. J. Biol. Chem. 253 (1978) 8854–8859. [PMID: 721818]
3.  Stevens, J.L. Isolation and characterization of a rat liver enzyme with both cysteine conjugate β-lyase and kynureninase activity. J. Biol. Chem. 260 (1985) 7945–7950. [PMID: 4008484]
4.  Stevens, J.L., Robbins, J.D. and Byrd, R.A. A purified cysteine conjugate β-lyase from rat kidney cytosol. Requirement for an α-keto acid or an amino acid oxidase for activity and identity with soluble glutamine transaminase K. J. Biol. Chem. 261 (1986) 15529–15537. [PMID: 3782077]
5.  Gaskin, P.J., Adcock, H.J., Buckberry, L.D., Teesdale-Spittle, P.H. and Shaw, P.N. The C-S lysis of L-cysteine conjugates by aspartate and alanine aminotransferase enzymes. Hum Exp Toxicol 14 (1995) 422–427. [DOI] [PMID: 7612304]
6.  Cooper, A.J., Bruschi, S.A., Iriarte, A. and Martinez-Carrion, M. Mitochondrial aspartate aminotransferase catalyses cysteine S-conjugate β-lyase reactions. Biochem. J. 368 (2002) 253–261. [DOI] [PMID: 12137566]
7.  Cooper, A.J., Bruschi, S.A., Conway, M. and Hutson, S.M. Human mitochondrial and cytosolic branched-chain aminotransferases are cysteine S-conjugate β-lyases, but turnover leads to inactivation. Biochem. Pharmacol. 65 (2003) 181–192. [DOI] [PMID: 12504794]
8.  Natsch, A., Schmid, J. and Flachsmann, F. Identification of odoriferous sulfanylalkanols in human axilla secretions and their formation through cleavage of cysteine precursors by a C-S lyase isolated from axilla bacteria. Chem. Biodivers. 1 (2004) 1058–1072. [DOI] [PMID: 17191898]
9.  Cooper, A.J. and Pinto, J.T. Cysteine S-conjugate β-lyases. Amino Acids 30 (2006) 1–15. [DOI] [PMID: 16463021]
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