Studies on the 12alpha and 26-hydroxylation of bile alcohols by rabbit liver microsomes

G NicolauE H Mosbach


12Alpha--Hydroxylation of two C27-steroids by rabbit liver microsomes was studied. Optimal assay conditions were determined with 7alpha-hydroxy-4-cholesten-3-one and 5beta-cholestand-3alpha, 7alpha-diol as substrates. The rate of 12alpha-hydroxylation of 7alpha-hydroxy-4-cholesten-3-one was found to be greater than that of 5beta-cholestane-3alpha, 7alpha-diol by ca. 60%. Microsomal 26-hydroxylation of 5beta-cholestane-3alpha7alpha-diol was also measured, and the ratio of 26-hydroxylation to 12alpha-hydroxylation of 5beta-cholestane-3alpha, 7alpha-diol was found to be ca. 0.4. Rabbit liver 12-alphahydroxylase was more active than that of three other species (man, rat, monkey), explaining in part the predominance of cholic acid in rabbit bile.


Jul 2, 1973·European Journal of Biochemistry·I Björkhem, J Gustafsson
Sep 30, 1974·Molecular and Cellular Biochemistry·I Björkhem, H Danielsson

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