EC 18.104.22.168 - Cystathionine β-lyase
IntEnz Enzyme Nomenclature
β C-S lyase
cystathionine L-homocysteine-lyase (deaminating)
L-cystathionine L-homocysteine-lyase (deaminating)
- (1) L-cystathionine + H2O = L-homocysteine + NH3 + pyruvate
- (1a) L-cystathionine + H2O = L-homocysteine + 2-aminoprop-2-enoate
- (1b) 2-aminoprop-2-enoate = 2-iminopropanoate (spontaneous)
- (1c) 2-iminopropanoate + H2O = pyruvate + NH3 (spontaneous)
A pyridoxal-phosphate protein. The enzyme cleaves a carbon-sulfur bond, releasing L-homocysteine 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. The enzyme from some sources also acts on L-cystine, forming pyruvate, ammonia and cysteine persulfide, and a number of related compounds. Possibly identical, in yeast, with EC 126.96.36.199 S-alkylcysteine lyase.
Links to other databases
Cystine lyase: β-cystathionase from turnip roots.Phytochemistry 18: 1953-1958 (1979).
Cystathionine cleavage enzymes of Neurospora.J. Biol. Chem. 239: 2212-2219 (1964). [PMID: 14209950]
[EC 188.8.131.52 created 1972]