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The substrate specificity and stereochemistry, reversibility and inhibition of the 3-oxo steroid delta 4-delta 5-isomerase component of cholesterol oxidase.

Authors
  • A G Smith
  • C J Brooks
Publication Date
Oct 01, 1977
Source
PMC
Keywords
Disciplines
  • Biology
License
Unknown

Abstract

1. 5-Cholesten-3-one was shown to be an intermediate in the conversion of cholesterol into 4-cholesten-3-one by Nocardia cholesterol oxidase. 2. The absence of a C-17 side chain from 5-androstene-3,17-dione slightly increased the Vmax. of the isomerase activity relative to 5-cholesten-3-one (1.7-fold), but greatly increased the Km. 3. Incubations of [4alpha-2H]-and [4beta-2H]-cholesterol with cholesterol oxidase showed that the 4beta-hydrogen atom can be transferred to the 6beta-position. However, incubations of cholesterol, 5-cholesten-3-one and 4-cholesten-3-one with the enzyme in 2H2O led to some incorporation of 2H into the 4-cholesten-3-one products, mostly at position 6beta. 4. Both the isomerase and the oxidase activities of cholesterol oxidase were inhibited by 5,10-seco-19-nor-5-cholestyne-3,10-dione.

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