This family is has been called MAPEG (Membrane Associated Proteins in Eicosanoid and Glutathione metabolism). It includes proteins such as Prostaglandin E synthase. This enzyme catalyses the synthesis of PGE2 from PGH2 (produced by cyclooxygenase from arachidonic acid). Because of structural similarities in the active sites of FLAP, LTC4 synthase and PGE synthase, substrates for each enzyme can compete with one another and modulate synthetic activity.

1: Common structural features of MAPEG -- a widespread superfamily of membrane associated proteins with highly divergent functions in eicosanoid and glutathione metabolism. Jakobsson PJ, Morgenstern R, Mancini J, Ford-Hutchinson A, Persson B; Protein Sci 1999;8:689-692. PMID:10091672