Cholesterol oxidase. Further studies of substrate specificity in relation to the analytical characterisation of steroids.

The substrate specificity of cholesterol oxidase has been further examined with respect to the size and shape of the steroid 17beta-side-chain and oxygenation of the nucleus. The relatively unreactive 17-keto-delta5-3beta-hydroxysteroids were converted to satisfactory substrates by formation of the isopentyl- or benzyloximes. The results obtained have been used to illustrate further uses of the enzyme in the gas-phase analytical characterisation and selective oxidation steroids. Oxidations were studied by kinetic experiments, gas-liquid chromatography-mass spectrometry.