title: Occurrence of cytochrome P-450 with prostaglandin omega-hydroxylase activity in rabbit placental microsomes.
abstract: The microsomes of placenta and uterus from pregnant rabbits have been found to catalyze the omega-hydroxylation of PGE1, PGE2, PGF2 alpha, and PGA1 as well as the omega- and (omega-1)-hydroxylation of palmitate and myristate in the presence of NADPH. These activities were greatly inhibited by carbon monoxide, indicating the involvement of cytochrome P-450. The apparent Km for PGE1 was 2.38 microM and 2.1 microM with the placental and uterus microsomes, respectively. Cytochrome P-450 has been solubilized with 1% cholate from the placental microsomes, and partially purified by chromatography on 6-amino-n-hexyl Sepharose 4B, DEAE-Sephadex A-50 and hydroxylapatite columns. The partially purified cytochrome P-450 efficiently catalyzed the omega-hydroxylation of various prostaglandins such as PGE1, PGE2, PGF2 alpha, PGD2, and PGA1 in a reconstituted system containing NADPH-cytochrome P-450 reductase, cytochrome b5, and phosphatidylcholine. The reconstituted system also hydroxylated palmitate and myristate at the omega- and (omega-1)-position, but could not hydroxylate laurate. These catalytic properties resemble those of a new form of cytochrome P-450 highly purified from the lung microsomes of progesterone-treated rabbits (Yamamoto, S., Kusunose, E., Ogita, K., Kaku, M., Ichihara, K., and Kusunose, M. (1984) J. Biochem. 96, 593-603). This type of cytochrome P-450, viz., cytochrome P-450 with high prostaglandin omega-hydroxylase activity may play a role in the regulation of prostaglandin levels in pregnancy.
mesh_terms: D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D005260:Female; D007700:Kinetics; D008861:Microsomes / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000302:isolation & purification / Q000378:metabolism*; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011817:Rabbits; D013379:Substrate Specificity
chemical_list: D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C026961:prostaglandin omega hydroxylases