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Oxidation of various simple steroids by the cholesterol oxidase system

1962; Elsevier BV; Volume: 97; Issue: 3 Linguagem: Inglês

10.1016/0003-9861(62)90111-x

1096-0384

Edmund Stevenson, Ezra Staple,

Cholesterol and Lipid Metabolism

Eight simple C24 steroids with C14 in the 26 position were synthesized. These compounds, which differ from one another in the A-ring substituents, were used to study the substrate specificity of the rat liver cholesterol oxidase system. The rate of C14O2 formation was taken as a measure of oxidation of the substrates. In both the cholestane and coprostane series, the oxidation rates fall in the ascending order: 3β-sterol, 3α-sterol, 3-ketone. Members of coprostane series are oxidized faster than the corresponding members of the cholestane series. There is an initial lag period in the oxidation of most of the substrates tested, during which little C14O2 is formed. Only coprostan-3-one-26-C14 and Δ4-cholesten-3-one-26-C14 are oxidized without this initial lag period. Cholesterol-26-C14 can be enzymically converted to a C27 3-ketone which is neither Δ4- nor Δ5-cholestenone, but which appears to differ from them in the number and position of double bonds. A 3-ketone without a 5α-hydrogen is hypothesized as an intermediate in the degradation of the cholesterol side chain by the cholesterol oxidase system.