Involved in cyanogenesis, the release of HCN from injured tissues (By similarity). Displays R-selective hydroxynitrile lyase activity. Also accepts nitromethane (MeNO2) as a donor in a reaction with aromatic aldehydes to yield (R)-beta-nitro alcohols. (R)-mandelonitrile = benzaldehyde + hydrogen cyanide Homodimer. Belongs to the AB hydrolase superfamily. Hydroxynitrile lyase family. Was originally thought to belong to the methylesterase (MES) family.