Homocysteine desulfhydrase

The enzyme homocysteine desulfhydrase (EC 4.4.1.2) catalyzes the chemical reaction


 * L-homocysteine + H2O = hydrogen sulfide + NH3 + 2-oxobutanoate (overall reaction)
 * (1a) L -homocysteine = hydrogen sulfide + 2-aminobut-2-enoate
 * (1b) 2-aminobut-2-enoate = 2-iminobutanoate (spontaneous)
 * (1c) 2-iminobutanoate + H2O = 2-oxobutanoate + NH3 (spontaneous)

This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is  L -homocysteine hydrogen-sulfide-lyase (deaminating; 2-oxobutanoate-forming). Other names in common use include homocysteine desulfurase, L -homocysteine hydrogen-sulfide-lyase (deaminating). This enzyme participates in nitrogen and sulfur metabolism. It employs one cofactor, pyridoxal phosphate.