Lyases;
Carbon-sulfur lyases;
Carbon-sulfur lyases (only sub-subclass identified to date)
BRITE hierarchy

L-cysteate hydrogensulfite-lyase (deaminating; pyruvate-forming)

L-cysteate + H2O = hydrogensulfite + pyruvate + NH3 (overall reaction) [RN:R07634];
(1a) L-cysteate = hydrogensulfite + 2-aminoprop-2-enoate;
(1b) 2-aminoprop-2-enoate = 2-iminopropanoate (spontaneous);
(1c) 2-iminopropanoate + H2O = pyruvate + NH3 (spontaneous)

R07634
Reaction

L-cysteate [CPD:C00506];
H2O [CPD:C00001];
2-aminoprop-2-enoate [CPD:C02218];
2-iminopropanoate [CPD:C20904]

A pyridoxal-phosphate protein. The enzyme cleaves a carbon-sulfur bond, releasing hydrogensulfite 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 3.5.99.10, 2-iminobutanoate/2-iminopropanoate deaminase. D-Cysteine can also act as a substrate, but more slowly. It is converted into hydrogen sulfide, pyruvate, and ammonia. This inducible enzyme from the marine bacterium Silicibacter pomeroyi DSS-3 forms part of the cysteate-degradation pathway.

EC 4.4.1.25 created 2006

1  [PMID:16302849]