Reaction: an S-alkyl-L-cysteine + H2O = an alkyl thiol + NH3 + pyruvate (overall reaction)
(1a) an S-alkyl-L-cysteine = an alkyl thiol + 2-aminoprop-2-enoate
(1b) 2-aminoprop-2-enoate = 2-iminopropanoate (spontaneous)
(1c) 2-iminopropanoate + H2O = pyruvate + NH3 (spontaneous)
Other name(s): S-alkylcysteinase; alkylcysteine lyase; S-alkyl-L-cysteine sulfoxide lyase; S-alkyl-L-cysteine lyase; S-alkyl-L-cysteinase; alkyl cysteine lyase; S-alkyl-L-cysteine alkylthiol-lyase (deaminating)
Systematic name: S-alkyl-L-cysteine alkyl-thiol-lyase (deaminating; pyruvate-forming)
Comments: A pyridoxal-phosphate protein. The enzyme cleaves a carbon-sulfur bond, releasing an alkyl thiol and an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form pyruvate and ammonia. The latter reaction, which can occur spontaneously, can also be catalysed by EC 22.214.171.124, 2-iminobutanoate/2-iminopropanoate deaminase. Possibly identical, in yeast, with EC 126.96.36.199 cystathionine β-lyase.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 62213-27-8
1. Nomura, J., Nishizuka, Y. and Hayaishi, O. S-Alkylcysteinase: enzymatic cleavage of S-methyl-L-cysteine and its sulfoxide. J. Biol. Chem. 238 (1963) 1441-1446.