title: Different suicide inactivation processes for the peroxidase and cyclooxygenase activities of prostaglandin endoperoxide H synthase-1.
abstract: Prostaglandin endoperoxide H synthases (PGHSs)-1 and -2 have a cyclooxygenase (COX) activity involved in forming prostaglandin G2 (PGG2) from arachidonic acid and an associated peroxidase (POX) activity that reduces PGG2 to PGH2. Suicide inactivation processes are observed for both POX and COX reactions. Here we report COX reaction conditions for PGHS-1 under which complete COX inactivation occurs but with > or = 60% retention of POX activity. The rates of POX inactivation were compared for native oPGHS-1 versus Y385F oPGHS-1, a mutant that cannot form the Tyr385 radical of COX Intermediate II; the rates were the same for both native and Y385F oPGHS-1. Our data indicate that a COX Intermediate II/acyl or product complex is the precursor in COX inactivation. However, another species, probably an Intermediate II-like species but with a radical centered on a tyrosine other than Tyr385, is the immediate precursor for POX inactivation.
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: I
authors.initials: I
authors.lastname: Song
authors.forename: T M
authors.initials: TM
authors.lastname: Ball
authors.forename: W L
authors.initials: WL
authors.lastname: Smith
mesh_terms: D000818:Animals; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D005227:Fatty Acids / Q000737:chemistry / Q000494:pharmacology; D005609:Free Radicals; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D010544:Peroxidases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D011451:Prostaglandin-Endoperoxide Synthases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics; D012756:Sheep; D014443:Tyrosine / Q000737:chemistry
chemical_list: D016861:Cyclooxygenase Inhibitors; D005227:Fatty Acids; D005609:Free Radicals; D007527:Isoenzymes; D011994:Recombinant Proteins; D014443:Tyrosine; D010544:Peroxidases; D011451:Prostaglandin-Endoperoxide Synthases