Involved in cyanogenesis, the release of HCN from injured tissues. Catalyzes the stereospecific addition of HCN to a variety of aldehydes in vitro. Has no oxidase activity. The redox properties of the FAD cofactor appear to be unimportant for catalysis. (R)-mandelonitrile = benzaldehyde + hydrogen cyanide Optimum pH is 5.5. Monomer. Glycosylated. Deglycosylation does not affect the enzymatic activity. Belongs to the GMC oxidoreductase family.