title: Prostaglandin hydroperoxidase, an integral part of prostaglandin endoperoxide synthetase from bovine vesicular gland microsomes.
abstract: The highly purified prostaglandin endoperoxide synthetase from bovine vesicular gland microsomes had two still unresolved enzyme activities; the oxygenative cyclization of 8,11,14-eicosatrienoic acid to produce prostaglandin G1 and the conversion of the 15-hydro-peroxide of prostaglandin G1 to a 15-hydroxyl group, producing prostaglandin H1. The latter enzymatic reaction required heme and was stimulated by a variety of compounds, including tryptophan, epinephrine, and guaiacol, but not by glutathione. A peroxidatic dehydrogenation was demonstrated with epinephrine or guaiacol in the presence of various hydroperoxides, including hydrogen peroxide and prostaglandin G1. Higher activity and affinity were observed with the 15-hydroperoxide of eicosapolyenoic acid, especially those with the prostaglandin structure. Both the dehydrogenation of epinephrine or guaiacol and the 15-hydroperoxide reduction of prostaglandin G1 were demonstrated in nearly stoichiometric quantities. With tryptophan, however, such a stoichiometric transformation was not observed. The peroxidase activity as followed with guaiacol and hydrogen peroxide and the tryptophan-stimulated conversion of prostaglandin G1 to H1 were not dissociable as examined by isoelectric focusing, heat treatment, pH profile, and heme specificity. The results suggest that the peroxidase with a broad substrate specificity is an integral part of prostaglandin endoperoxide synthetase which is responsible for the conversion of prostaglandin G1 to H1.
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000494:pharmacology; D002417:Cattle; D004355:Drug Stability; D006427:Hemin / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D009097:Multienzyme Complexes / Q000302:isolation & purification / Q000378:metabolism*; D010544:Peroxidases; D011451:Prostaglandin-Endoperoxide Synthases / Q000302:isolation & purification / Q000378:metabolism*; D012669:Seminal Vesicles / Q000201:enzymology*; D013053:Spectrophotometry
chemical_list: D009097:Multienzyme Complexes; D006427:Hemin; D002248:Carbon Monoxide; C022464:prostaglandin hydroperoxidase; D010544:Peroxidases; D011451:Prostaglandin-Endoperoxide Synthases