title: O-acetylsalicylhydroxamic acid, a novel acetylating inhibitor of prostaglandin H2 synthase: structural and functional characterization of enzyme-inhibitor interactions.
abstract: Aspirin is unique among clinically used nonsteroidal antiinflammatory drugs in that it irreversibly inactivates prostaglandin (PG) H2 synthase (PGHS) via acetylation of an active-site serine residue. We report the synthesis and characterization of a novel acetylating agent, O-acetylsalicylhydroxamic acid (AcSHA), which inhibits PGE2 synthesis in vivo and blocks the cyclooxygenase activity of PGHS in vitro. AcSHA requires the presence of the active-site residue Ser-529 to be active against human PGHS-1; the S529A mutant is resistant to inactivation by the inhibitor. Analysis of PGHS inactivation by AcSHA, coupled with the X-ray crystal structure of the complex of ovine PGHS-1 with AcSHA, confirms that the inhibitor elicits its effects via acetylation of Ser-529 in the cyclooxygenase active site. The crystal structure reveals an intact inhibitor molecule bound in the enzyme's cyclooxygenase active-site channel, hydrogen bonding with Arg-119 of the enzyme. The structure-activity profile of AcSHA can be rationalized in terms of the crystal structure of the enzyme-ligand complex. AcSHA may prove useful as a lead compound to facilitate the development of new acetylating inhibitors.
authors.affiliation: Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Loll
authors.forename: C T
authors.initials: CT
authors.lastname: Sharkey
authors.forename: S J
authors.initials: SJ
authors.lastname: O'Connor
authors.forename: C M
authors.initials: CM
authors.lastname: Dooley
authors.forename: E
authors.initials: E
authors.lastname: O'Brien
authors.forename: M
authors.initials: M
authors.lastname: Devocelle
authors.forename: K B
authors.initials: KB
authors.lastname: Nolan
authors.forename: B S
authors.initials: BS
authors.lastname: Selinsky
authors.forename: D J
authors.initials: DJ
authors.lastname: Fitzgerald
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000818:Animals; D001120:Arginine / Q000378:metabolism; D001665:Binding Sites / Q000502:physiology; D019556:COS Cells; D003460:Crystallization; D018360:Crystallography, X-Ray; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D008565:Membrane Proteins; D016297:Mutagenesis, Site-Directed; D010974:Platelet Aggregation / Q000187:drug effects; D011451:Prostaglandin-Endoperoxide Synthases / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D011487:Protein Conformation; D012457:Salicylamides / Q000494:pharmacology*; D012694:Serine / Q000378:metabolism
chemical_list: D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; C441521:O-acetylsalicylhydroxamic acid; D012457:Salicylamides; D012694:Serine; D001120:Arginine; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases