The enzyme contains Zn2+?[1]. The enzyme catalyses the stereoselective synthesis of aliphatic (R)-cyanohydrins [1]. No activity towards mandelonitrile and 4-hydroxymandelonitrile [5]. Natural substrates for the (R)-oxynitrilase from?Linum usitatissimum?are acetone and butan-2-one, which are the building blocks of the cyanogen glycosides in?Linum, linamarin and lotaustralin, or linustatin and neolinustatin, respectively [4].