Improved purification of an (R)‐oxynitrilase from Linum usitatissimum (flax) and investigation of the substrate range

The purification of (R)-oxynitrilase (EC 4.1.2.10) from Linum usitatissimum (flax) has been improved considerably. The enzyme is obtained from seedlings in 60% yield by fractional salt precipitation followed by ion-exchange and hydrophobic-interaction chromatography. Final gel-permeation chromatography yields a protein with a specific activity of 53 units/mg at pH 4.1. The N-terminal sequence is reported and microheterogeneity demonstrated. The substrate range was investigated using (R)-oxynitrilase immobilized on Eupergit and t-butyl methyl ether as solvent. The addition of HCN to various aliphatic ketones and aldehydes is catalysed by the enzyme, while aromatic ketones are not converted. (R)-Butan-2-one cyanohydrin was synthesized on a preparative scale and the product characterized.