MODIFICATION OF BREVIBACTERIUM-STEROLICUM CHOLESTEROL OXIDASE AND SUBSTRATE-SPECIFICITY

Cholesterol oxidase modified by hydrogen peroxide is inactive with cho lesterol solubilized in buffer with surfactants. Pregn-5-en-3beta-ol w hen solubilized in the same conditions and substrates soluble in buffe r, like 3beta-hydroxy-androst-5-en-17-one or 3beta-hydroxy-androst-5-e n-17beta-carboxylic acid are substrates of the modified enzyme. The ob served loss of activity on cholesterol could be due to the inability o f the oxidized cholesterol oxidase to extract cholesterol from mixed c holesterol/surfactant aggregates. Cholesterol oxidase on storage under goes modifications close to those with hydrogen peroxide and care shou ld be taken for the use of cholesterol oxidase as cholesterol probe.