Studies on the 12alpha and 26-hydroxylation of bile alcohols by rabbit liver microsomes.
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.
D000438:Alcohols / Q000378:metabolism; D000818:Animals; D001646:Bile / Q000378:metabolism*; D002776:Cholestanes / Q000138:chemical synthesis / Q000378:metabolism*; D002782:Cholestenes / Q000378:metabolism*; D002783:Cholestenones / Q000138:chemical synthesis / Q000378:metabolism*; D005260:Female; D000882:Haplorhini; D006801:Humans; D006900:Hydroxylation; D007700:Kinetics; D008253:Macaca mulatta; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D013045:Species Specificity; D013250:Steroid Hydroxylases / Q000378:metabolism*; D013261:Sterols / Q000378:metabolism
D000438:Alcohols; D002776:Cholestanes; D002782:Cholestenes; D002783:Cholestenones; D011506:Proteins; D013261:Sterols; C002656:7 alpha-hydroxy-4-cholesten-3-one; D013250:Steroid Hydroxylases