EC 4.4.1.1 - Cystathionine γ-lyase
IntEnz view
ENZYME view
IntEnz Enzyme Nomenclature
EC 4.4.1.1
Names
Accepted name:
cystathionine γ-lyase
Other
names:
γ-CTL
γ-cystathionase
cystalysin
cystathionase
cysteine desulfhydrase
cysteine lyase
cystine desulfhydrase
homoserine deaminase
homoserine deaminase-cystathionase
homoserine dehydratase
cystathioninase
L-cystathionine cysteine-lyase (deaminating)
γ-cystathionase
cystalysin
cystathionase
cysteine desulfhydrase
cysteine lyase
cystine desulfhydrase
homoserine deaminase
homoserine deaminase-cystathionase
homoserine dehydratase
cystathioninase
L-cystathionine cysteine-lyase (deaminating)
Systematic name:
L-cystathionine cysteine-lyase (deaminating; 2-oxobutanoate-forming)
Reactions
- (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)
Cofactor
Comments:
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 3.5.99.10, 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
Enzymes and pathways:
NC-IUBMB
,
BRENDA
,
DIAGRAM
,
ExplorEnz
,
ENZYME@ExPASy
,
KEGG
,
MetaCyc
,
UniPathway
Protein domains and families:
PROSITE:PDOC00677
CAS Registry Number:
9012-96-8
References
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[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).
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[Phosphopyridoxal in aerobic deamination of homoserine and serine.] (in Russian)Dokl. Akad. Nauk. S.S.S.R. 85 : 385-388 (1952).
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Purification and properties of the cystathionine γ-cleavage enzyme of Neurospora.J. Biol. Chem. 239 : 2220-2227 (1964). [PMID: 14209951]
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A crystalline enzyme that cleaves homoserine and cystathionine. III. Coenzyme resolution, activation, and inhibitors.J. Biol. Chem. 234 : 507-515 (1959). [PMID: 13641250]
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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 4.4.1.1 created 1961 (EC 4.2.1.15 created 1961, incorporated 1972)]