EC 22.214.171.124 - Cystathionine γ-lyase
IntEnz Enzyme Nomenclature
L-cystathionine cysteine-lyase (deaminating)
- (1) L-cystathionine + H2O = L-cysteine + NH3 + 2-oxobutanoate
- (1a) L-cystathionine = L-cysteine + 2-aminobut-2-enoate
- (1b) 2-aminobut-2-enoate = 2-iminobutanoate (spontaneous)
- (1c) 2-iminobutanoate + H2O = 2-oxobutanoate + NH3 (spontaneous)
A multifunctional pyridoxal-phosphate protein. The enzyme cleaves a carbon-sulfur bond, releasing L-cysteine and an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form 2-oxobutanoate and ammonia. The latter reaction, which can occur spontaneously, can also be catalysed by EC 126.96.36.199, 2-iminobutanoate/2-iminopropanoate deaminase. Also catalyses the conversion of L-homoserine to 2-oxobutanoate and ammonia, of L-cystine to thiocysteine, pyruvate and ammonia, and of L-cysteine to pyruvate, hydrogen sulfide and ammonia.
Links to other databases
[Participation of vitamin B6 in enzymic formation of hydrogen sulfide from L-cysteine.] (in Russian)Dokl. Akad. Nauk. S.S.S.R. 71: 93-96 (1950).
[Phosphopyridoxal in aerobic deamination of homoserine and serine.] (in Russian)Dokl. Akad. Nauk. S.S.S.R. 85: 385-388 (1952).
Purification and properties of the cystathionine γ-cleavage enzyme of Neurospora.J. Biol. Chem. 239: 2220-2227 (1964). [PMID: 14209951]
A crystalline enzyme that cleaves homoserine and cystathionine. III. Coenzyme resolution, activation, and inhibitors.J. Biol. Chem. 234: 507-515 (1959). [PMID: 13641250]
A crystalline enzyme that cleaves homoserine and cystathionine. IV. Mechanism of action, reversibility, and substrate specificity.J. Biol. Chem. 234: 516-519 (1959). [PMID: 13641251]
[EC 188.8.131.52 created 1961 (EC 184.108.40.206 created 1961, incorporated 1972)]