Mechanism of FANFT cooxidation by prostaglandin endoperoxide synthetase
Zenser, T.V.; Mattammal, M.B.; Davis, B.B.
Journal of Pharmacology and Experimental Therapeutics 214(2): 312-317
1980
ISSN/ISBN: 0022-3565 PMID: 6771392 Document Number: 163053
The cooxidative metabolism of N- by the fatty acid cyclooxygenase or hydroperoxidase activities of prostaglandin endoperoxide synthetase was examined by using solubilized microsomes prepared from the rabbit renal inner medulla and ram seminal vesicle. Metabolism was measured by the rate of decrease in absorbancy at 400 nm. Cooxidative metabolism of FANFT was initiated by arachidonic acid, 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid, cumene hydroperoxide and tert-butyl hydroperoxide. This cooxidation was inhibited by radical scavengers such as ethoxyquin, butylated hydroxytoluene and vitamin E. Indomethacin inhibited arachidonic acid-mediated FANFT metabolism but not cumene hydroperoxide-mediated FANFT metabolism or prostaglandin hydroperoxidase activity. Ferric heme was required for cooxidation of FANFT. With manganese heme, arachidonic acid metabolism by fatty acid cyclooxygenase was observed but cooxidation did not occur. Cooxidation did not occur with protoporphyrin IX or FeCl3. The efficiencies of FANFT cooxidation by arachidonic acid, cumene hydroperoxide or 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid were similar (.apprx. 58%). Cumene hydroperoxide- and arachidonic acid-mediated FANFT cooxidation were blocked in the absence of oxygen. KCN and NaN3 inhibited FANFT cooxidation and hydroperoxidase activity to a similar extent. FANFT cooxidation apparently is mediated by the hydroperoxidase activity of prostaglandin endoperoxide synthetase. Molecular oxygen also appears to play a role in FANFT cooxidation independent of hydroperoxidase.