Reaction: L-cysteine + H2O = sulfide + NH3 + pyruvate (overall reaction)
(1a) L-cysteine = 2-aminoprop-2-enoate + sulfide
(1b) 2-aminoprop-2-enoate = 2-iminopropanoate (spontaneous)
(1c) 2-iminopropanoate + H2O = pyruvate + NH3 (spontaneous)
Other name(s): L-cysteine desulfhydrase
Systematic name: L-cysteine sulfide-lyase (deaminating; pyruvate-forming)
Comments: The enzyme from the archaeon Methanocaldococcus jannaschii contains a [4Fe-4S] cluster and is specific for L-cysteine (cf. EC 4.4.1.1, cystathionine γ-lyase). It cleaves a carbon-sulfur bound releasing sulfide and the unstable enamine product 2-aminoprop-2-enoate that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form pyruvate and ammonia. The same reaction can also be catalysed by some pyridoxal-phosphate proteins (cf. EC 4.4.1.1, cystathionine γ-lyase).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number:
References:
1. Tchong, S.I., Xu, H. and White, R.H. L-Cysteine desulfidase: an [4Fe-4S] enzyme isolated from Methanocaldococcus jannaschii that catalyzes the breakdown of L-cysteine into pyruvate, ammonia, and sulfide. Biochemistry 44 (2005) 1659-1670. [PMID: 15683250]