PT - JOURNAL ARTICLE AU - Joseph A. Mancini AU - Philip J. Vickers AU - Gary P. O’Neill AU - Catherine Boily AU - Jean-Pierre Falgueyret AU - Denis Riendeau TI - Altered Sensitivity of Aspirin-Acetylated Prostaglandin G/H Synthase-2 to Inhibition by Nonsteroidal Anti-Inflammatory Drugs AID - 10.1124/mol.51.1.52 DP - 1997 Jan 01 TA - Molecular Pharmacology PG - 52--60 VI - 51 IP - 1 4099 - http://molpharm.aspetjournals.org/content/51/1/52.short 4100 - http://molpharm.aspetjournals.org/content/51/1/52.full SO - Mol Pharmacol1997 Jan 01; 51 AB - Aspirin (ASA) acetylates Ser516 of prostaglandin G/H synthase-2 (PGHS-2) resulting in a modified enzyme that converts arachidonic acid to 15(R)-hydroxy-eicosatetraenoic acid [15(R)-HETE]. ASA has pharmacological benefits that may not all be limited to inhibition of prostaglandin synthesis, and this study was initiated to further investigate the properties of ASA-acetylated PGHS-2 and of the mutation of Ser516 to methionine, which mimics ASA acetylation. Both the S516M mutant and ASA-acetylated form of PGHS-2 (ASA-PGHS-2) synthesize 15(R)-HETE and have apparent K m values for arachidonic acid within 10-fold of the apparentK m value for untreated PGHS-2. The time courses of turnover-dependent inactivation were similar for reactions catalyzed by PGHS-2 and ASA-PGHS-2, whereas the PGHS-2(S516M) showed a decrease in both the initial rate of 15-HETE production and rate of enzyme inactivation. The production of 15-HETE by modified PGHS-2 was sensitive to inhibition by most nonsteroidal anti-inflammatory drugs (NSAIDs), including selective PGHS-2 inhibitors. As observed for the cyclooxygenase activity of PGHS-2, the inhibition of 15-HETE production by indomethacin was time-dependent for both ASA-PGHS-2 and PGHS-2(S516M). However, two potent, structurally related NSAIDs, diclofenac and meclofenamic acid, do not inhibit either ASA-PGHS-2 or the PGHS-2(S516M) mutant. These results demonstrate that the sensitivity to inhibition by NSAIDs of the 15-HETE production by ASA-treated PGHS-2 is different than that of prostaglandin production by PGHS-2 and that Ser516 plays an important role in the interaction with fenamate inhibitors. The results also indicate that the conversion of arachidonic acid to 15-HETE by ASA-PGHS-2 is an efficient process providing a unique mechanism among NSAIDs that will not lead to arachidonic acid accumulation or shunting to other biosynthetic pathways.