title: Cyclooxygenase and peroxidase inactivation of prostaglandin-H-synthase during catalysis.
abstract: Prostaglandin-H-synthase (PGHS) is a bifunctional enzyme catalyzing cyclooxygenase and peroxidase reactions and undergoing irreversible inactivation during catalysis. A new method for kinetic studies of both PGHS activities in the course of cyclooxygenase as well as peroxidase reactions and also preincubation with hydroperoxides is suggested. It is shown that peroxidase activity is retained after complete cyclooxygenase inactivation and cyclooxygenase activity is retained after complete peroxidase inactivation. Two-stage cyclooxygenase inactivation occurs on preincubation of PGHS with hydrogen peroxide. Studies on inactivation under various conditions indicate that chemical mechanisms of cyclooxygenase and peroxidase inactivation are different. The data allow development of kinetic models.
authors.affiliation: Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119992, Russia.
authors.forename: L A
authors.initials: LA
authors.lastname: Tsaplina
authors.forename: P V
authors.initials: PV
authors.lastname: Vrzheshch
mesh_terms: D000818:Animals; D002384:Catalysis; D006861:Hydrogen Peroxide / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D009195:Peroxidase / Q000037:antagonists & inhibitors*; D011451:Prostaglandin-Endoperoxide Synthases / Q000737:chemistry*
chemical_list: D006861:Hydrogen Peroxide; D009195:Peroxidase; D011451:Prostaglandin-Endoperoxide Synthases