Stero-bile Acids and Bile Alcohols:CV. Conversion of 7α, 12α-Dihydroxycholest-4-en-3-one to 5α-Cyprinol by Carp Liver

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The formation of 5α-cyprinol from 7α, 12α-dihydroxycholest-4-en-3-one was investi-gated in vitro with a carp liver preparation.<br> 1. The results indicate that a major pathway in this conversion is: 7α, 12α-dihy-droxycholest-4-en-3-one→5α-cholestane-3α, 7α, 12α-triol→deoxy-5α-cyprinol→5α-cyprinol.<br> 2. The microsomal fraction of carp liver catalyzed the transformation of 7α, 12α-dihydroxycholest-4-en-3-one to 5α-cholestane-3α, 7α, 12α-trios. The supernatant obtained by high speed centrifugation and the mitochondrial fraction of carp liver did not reduce this Δ4-3-keto compound to any measurable extent. The microsomal enzyme system required NADPH as a hydrogen donor and was inactive in the presence of NADH.<br> 3. In the presence of the microsomal fraction 5α- and 5β-cholestane-3α, 7α, 12α-triols were converted to deoxy-5α-cyprinol and 5β-cholestane-3α, 7α, 12α, 26-tetrol, respectively. The hydroxylase required NADPH as cofactor. The supernatant obtained by high speed centrifugation and the mitochondrial fraction did not catalyze the hydroxylation of these trials.<br> 4. The conversion of deoxy-5α-cyprinol to 5α-cyprinol was catalyzed by the mito-chondria) fraction fortified with NADPH but not by the microsomal fraction or the supernatant obtained by high 'peed centrifugation.

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