Animal prostaglandin endoperoxide synthase and related bacterial proteins
Animal prostaglandin endoperoxide synthases, including prostaglandin H2 synthase and a set of similar bacterial proteins which may function as cyclooxygenases. Prostaglandin H2 synthase catalyzes the synthesis of prostaglandin H2 from arachidonic acid. In two reaction steps, arachidonic acid is converted to Prostaglandin G2, a peroxide (cyclooxygenase activity) and subsequently converted to the end product via the enzyme's peroxidase activity. Prostaglandin H2 synthase is the target of aspirin and other non-steroid anti-inflammatory drugs such as ibuprofen, which block the substrate's access to the active site and may acetylate a conserved serine residue. In humans and other mammals, prostaglandin H2 synthase (PGHS), also called cyclooxygenase (COX) is present as at least two isozymes, PGHS-1 (or COX-1) and PGHS-2 (or COX-2), respectively. PGHS-1 is expressed constitutively in most mammalian cells, while the expression of PGHS-2 is induced via inflammation response in endothelial cells, activated macrophages, and others. COX-3 is a splice variant of COX-1.
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