Mutation of serine‐516 in human prostaglandin G/H synthase‐2 to methionine or aspirin acetylation of this residue stimulates 15‐R‐HETE synthesis

Abstract

Prostaglandin G/H synthase (PGHS) is a key enzyme in cellular prostaglandin (PG) synthesis and is the target of non‐steroidal anti‐inflammatory agents. PGHS occurs in two isoforms, termed PGHS‐1 and PGHS‐2. These isoforms differ in several respects, including their enzymatic activity following acetylation by aspirin. While PG synthesis by both isoforms is inhibited by aspirin, 15‐R‐hydroxyeicosatetraenoic acid (15‐R‐HETE) synthesis by PGHS‐2, but not PGHS‐1, is stimulated by preincubation with aspirin. We have mutated the putative aspirin acetylation site of hPGHS‐2, and expressed the mutants in COS‐7 cells using recombinant vaccinia virus. Enzyme activity and inhibitor sensitivity studies provide evidence that Ser⁵¹⁶ is the aspirin acetylation site of human PGHS‐2 and that substitution of a methionine residue at this position can mimic the effects of aspirin acetylation on enzyme activity.