In enzymology, glycine dehydrogenase (cyanide-forming) () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are glycine and an electron acceptor. Its products are hydrogen cyanide, carbon dioxide, and reduced acceptor.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH<sub>2</sub> group of donors with other acceptors. The systematic name of this enzyme class is glycine:acceptor oxidoreductase (hydrogen-cyanide-forming). Other names in common use include hydrogen cyanide synthase, and HCN synthase.