Isolation of cytochrome P-450 highly active in prostaglandin omega-hydroxylation from lung microsomes of rabbits treated with progesterone.
Two forms of cytochrome P-450, designated as cytochrome P-450p-1 and cytochrome P-450p-2, were separated and purified to specific contents of 8.2 and 8.9 nmol/mg of protein, respectively, from lung microsomes of rabbits treated with progesterone. Cytochrome P-450p-1 and cytochrome P-450p-2 migrated as single polypeptide bands with molecular weights of 49,000 and 52,000, respectively, on SDS-polyacrylamide gel. Their CO-reduced difference spectral peaks were at 451.5 and 450 nm, respectively. Cytochrome P-450p-1 catalyzed the N-demethylation of benzphetamine, O-demethylation of p-nitroanisole, and O-deethylation of 7-ethoxycoumarin, whereas no activity was observed with cytochrome P-450p-2. On the other hand, cytochrome P-450p-2 catalyzed the omega-hydroxylation of prostaglandin E1 (PGE1), prostaglandin E2 (PGE2), and prostaglandin A1 (PGA1) with turnover rates of 9.0, 7.5, and 5.0 nmol of product/min/nmol of cytochrome P-450, respectively, as well as the omega- and (omega-1)-hydroxylation of palmitate and myristate with turnover rates of 27.7 and 16.4 nmol products/min/nmol of cytochrome P-450, respectively. This cytochrome showed a greater affinity for prostaglandins (PGs) than for fatty acids. These reactions were absolutely dependent on cytochrome P-450p-2 and NADPH-cytochrome P-450 reductase, and stimulated by addition of phosphatidylcholine and cytochrome b5. Cytochrome P-450p-2 is thought to be a new form of cytochrome P-450 induced by progesterone treatment in rabbit lung microsomes.
D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005260:Female; D006900:Hydroxylation; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000378:metabolism; D008970:Molecular Weight; D011374:Progesterone / Q000494:pharmacology*; D011453:Prostaglandins / Q000378:metabolism*; D011817:Rabbits; D013379:Substrate Specificity
D005230:Fatty Acids, Nonesterified; D011453:Prostaglandins; D011374:Progesterone; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases