Prostaglandin E synthase (PGES) catalyzes the isomerization of PGH2 to PGE2 . Cytosolic and microsomal PGES enzymes have been cloned and characterized. Cytosolic PGES (cPGES) is a glutathione-dependent enzyme with a predicted size of 18.6 kDa (23 kDa on SDS-PAGE). The enzyme is expressed in a wide variety of tissues and cells, the levels of which are unaffected by treatment with IL-1β and TNF-α. However, enzyme expression increases approximately 3-fold in rat brain following LPS treatment. Microsomal PGES (mPGES) is a 16 kDa protein expressed in a variety of tissues including prostate, testes, and small intestine, as well as in A549 and HeLa cells. In contrast to cPGES, mPGES protein expression is increased in A549 cells following treatment with IL-1β. The two enzymes show <10% homology at the amino acid level.
