IUBMB Enzyme Nomenclature


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): L-cysteine-S-conjugate thiol-lyase (deaminating; 2-aminoprop-2-enoate-forming)

Systematic name: L-cysteine-S-conjugate thiol-lyase (deaminating; pyruvate-forming)

Comments: A pyridoxal-phosphate protein. The enzyme can act on a broad range of L-cysteine-S-conjugates, including aromatic conjugates such as 4-bromobenzene and 2,4-dinitrobenzene. 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. The latter reaction, which can occur spontaneously, can also be catalysed by EC, 2-iminobutanoate/2-iminopropanoate deaminase.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 68652-57-3


1. 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]

[EC created 1981]

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