 To date, microsomal prostaglandin E synthase-1 emerges as a key enzyme in the formation of PGE2.Terminal prostaglandin synthases have been identified that are responsible for the formation of other prostaglandins.For example, hematopoietic and lipocalin prostaglandin D synthases (hPGDS and lPGDS) are responsible for the formation of PGD2 from PGH2.