Isomerase that catalyzes the conversion of PGH2 into the more stable prostaglandin E2 (PGE2) (in vitro). The biological function and the GSH-dependent property of PTGES2 is still under debate (By similarity). In vivo, PTGES2 could form a complex with GSH and heme and would not participate in PGE2 synthesis but would catalyze the degradation of prostaglandin E2 H2 (PGH2) to 12(S)-hydroxy-5(Z),8(E),10(E)-heptadecatrienoic acid (HHT) and malondialdehyde (MDA) (By similarity). prostaglandin H2 = prostaglandin E2 prostaglandin H2 = (12S)-hydroxy-(5Z,8E,10E)-heptadecatrienoate + malonaldehyde Isomerase activity is increased by sulfhydril compounds. Dithiothreitol (DTT) is most effective, followed by glutathione (GSH) and 2-mercaptoethanol. Lipid metabolism; prostaglandin biosynthesis. Homodimer. Belongs to the GST superfamily.