title: Cytochromes P-450 LM3b and LM4 in biosynthesis of bile acids.
abstract: Cytochromes P-450 LM3b and LM4 were prepared from untreated and cholestyramine-treated rabbits. The catalytic properties of these cytochrome P-450 fractions towards substrates in bile acid biosynthesis were studied in reconstituted systems containing NADPH -- cytochrome P-450 reductase and phospholipid. Cytochrome P-450 LM3b showed no hydroxylase activity towards cholesterol and only low activity towards some other C27-steroids whereas it catalyzed efficient hydroxylation of testosterone and demethylation of ethylmorphine. Preparations of cytochrome P-450 LM4 catalyzed hydroxylation of cholesterol and other C27-steroids more efficiently than microsomes. Cytochrome b5 had no stimulatory effect on the C27-steroid hydroxylase activities.
mesh_terms: D000818:Animals; D001647:Bile Acids and Salts / Q000096:biosynthesis*; D002784:Cholesterol / Q000378:metabolism; D002792:Cholestyramine Resin / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003580:Cytochromes / Q000378:metabolism; D015786:Cytochromes b5; D006900:Hydroxylation; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D008970:Molecular Weight; D011817:Rabbits; D013739:Testosterone / Q000378:metabolism
chemical_list: D001647:Bile Acids and Salts; D003580:Cytochromes; D002792:Cholestyramine Resin; D013739:Testosterone; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; D002784:Cholesterol