A form of rabbit liver cytochrome P-450 that catalyzes the 7 alpha-hydroxylation of cholesterol.
A form of cytochrome P-450 which comigrates with cytochrome P-450LM4 (molecular weight, 55 000) on SDS-polyacrylamide gel was purified from liver microsomes of cholestyramine-treated rabbits. This form of cytochrome P-450 catalyzed the 7 alpha-hydroxylation of cholesterol with an activity of 37.5 pmol/min per nmol cytochrome P-450 in the reconstituted enzyme system containing cytochrome P-450 and NADPH-cytochrome P-450 reductase. The substrate specificity of this form of cytochrome P-450 was compared with cytochrome P-450LM4 isolated from phenobarbital- and beta-naphthoflavone-treated rabbit liver microsomes. The latter two isoenzymes do not catalyze 7 alpha-hydroxylation of cholesterol, but are more active in O-deethylation of 7-ethoxycoumarin and p-nitrophenetole. Ouchterlony double diffusion revealed cross-reactivity between anti-P-450LM4 (phenobarbital) IgG and cytochrome P-450 isolated from cholestyramine- or beta-naphthoflavone-treated rabbit liver microsomes. A two-dimensional iodinated tryptic peptide fingerprint indicated only minor structural differences among these three cytochrome P-450LM4 preparations.
D000818:Animals; D002784:Cholesterol / Q000378:metabolism*; D002792:Cholestyramine Resin / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D006900:Hydroxylation; D005779:Immunodiffusion; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D008970:Molecular Weight; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D011817:Rabbits; D013379:Substrate Specificity
D007527:Isoenzymes; D002792:Cholestyramine Resin; D003577:Cytochrome P-450 Enzyme System; D002784:Cholesterol; D009251:NADPH-Ferrihemoprotein Reductase