Multiple forms of cytochrome P-450 from kidney cortex microsomes of rabbits treated with phenobarbital.
Two distinct forms of cytochrome P-450 (P-450), referred to as P-450a and P-450b, were separated and purified from kidney cortex microsomes of rabbits treated with phenobarbital. P-450a had a monomeric molecular weight of 53,000, and its CO-reduced difference spectral peak was at 450 nm. It catalyzed the omega-hydroxylation of prostaglandin A1 (PGA1), and the omega- and (omega-1)-hydroxylation of myristate, but it was inactive toward exogenous compounds tested. On the other hand, P-450b had a monomeric molecular weight of 49,000, and its CO-reduced difference spectral peak was at 451 nm. This cytochrome was not able to hydroxylate PGA1 at all. It hydroxylated myristate much more slowly than P-450a, and preferentially at the (omega-1)-position. Unlike P-450a, P-450b efficiently metabolized exogenous compounds such as benzphetamine, aminopyrine, 7-ethoxycoumarin and p-nitroanisole. It is suggested that P-450a and P-450b are specialized for the metabolism of PGA1 and exogenous compounds, respectively, in kidney cortex microsomes.
D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis / Q000302:isolation & purification*; D003573:Cytochrome b Group / Q000032:analysis; D015786:Cytochromes b5; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000032:analysis; D007672:Kidney Cortex / Q000201:enzymology*; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000032:analysis; D010634:Phenobarbital / Q000494:pharmacology*; D011817:Rabbits
D003573:Cytochrome b Group; D007527:Isoenzymes; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; D009251:NADPH-Ferrihemoprotein Reductase; D010634:Phenobarbital