Hematopoietic Prostaglandin D Synthase (HPGDS) belongs to the GST superfamily and Sigma family. HPGDS contains one GST C-terminal domain and one GST N-terminal domain. HPGDS is highly expressed in adipose tissue, macrophages, and placenta, and it exists in the form of homodimer in living body. HPGDS is a cytosolic enzyme that isomerizes PGH(2). HPGDS is a bifunctional enzyme that catalyzes both the conversion of PGH2 to PGD2 and also shows low glutathione-peroxidase activity towards cumenehydroperoxide.