In enzymology, a L-3-cyanoalanine synthase (EC 4.4.1.9) is an enzyme that catalyzes the chemical reaction
- L-cysteine + hydrogen cyanide L-3-cyanoalanine + hydrogen sulfide
Thus, the two substrates of this enzyme are L-cysteine and hydrogen cyanide, whereas its two products are L-3-cyanoalanine and hydrogen sulfide.
This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is L-cysteine hydrogen-sulfide-lyase (adding hydrogen cyanide L-3-cyanoalanine-forming). Other names in common use include beta-cyanoalanine synthase, beta-cyanoalanine synthetase, beta-cyano-L-alanine synthase, and L-cysteine hydrogen-sulfide-lyase (adding HCN). This enzyme participates in cyanoamino acid metabolism.