[Study of the specificity of action of cholesterol oxygen oxidoreductase on various sterols and related substances].

The authors studied the action of oxygen cholesterol oxidoreductase (E.C. 1.1.3.6) extracted from Nocardia erythropolis on different sterols following simultaneously:--the disappearance of the substrate by chromatography on thin layers of silic acid, the formation of hydrogen peroxide by Röschlau's reaction, changes in the absorption spectrum between 220 and 320 nm. The results obtained show that sterol oxidase presents a broad spectrum of activity. It catalyses the transformation into ketone of the secondary alcohol group at the 3 beta position of sterols which possess in the C17 position a lateral chain of at least two carbon atoms. In the other hand, the reaction does not take place if there exists in the C5 position, an H in the cis position or if two hydrogen atoms linked to carbon 4 are substituted. Finally, only oxidation products derived from sterols possess a double bond situated in the 4-5 or 5-6 position presenting an absorption band between 240 and 250 nm.