[Prostaglandin E2 synthases].

Prostaglandin E2 (PGE2) is widely distributed in various tissues, and exhibits various biologically important activities. PGE2 synthase (PGES) catalyzes conversion of COX-derived PGH2 to PGE2. It now appears that there are at least three distinct types of PGES in mammals. We identified two distinct glutathione-dependent PGESs. Cytosolic PGES (cPGES), known as p23, is constitutively and ubiquitously expressed and predominantly converts COX-1-derived PGH2 to PGE2. We find that the regulation of cPGES/p23 activity in cells depends on its association with hsp90. Microsomal PGES-1 (mPGES-1), identical to MGST1-L1, is an inducible perinuclear enzyme that is functionally linked with COX-2 in marked preference to COX-1. COX-2 and mPGES-1 are essential components for delayed PGE2 synthesis, which may be linked to inflammation, fever, osteogenesis, and even cancer. Most recently, glutathione-nonspecific mPGES-2, homologous to glutaredoxin and thioredoxin, was identified. These PGESs seem to be a potential novel target for drug development.