Prostaglandin D synthase (PGDS) catalyzes the isomerization of PGH2 to produce PGD2. PGD2 induces sleep, regulates nociception, inhibits platelet aggregation and acts as an allergic mediator. Two distinct types of PGDS have been identified, namely the lipocalin-type enzyme (β-trace) and the hematopoietic enzyme.1,2,3 Lipocalin-type PGDS is localized in the central nervous system and male genital organs of various mammals and the human heart. This enzyme has been identified as β-trace, which is a major protein in human cerebrospinal fluid.1 The recombinant human L-PGDS was expressed and purified from E.Coli as a 47.5 kDa glutathione S-transferase (GST)-fusion protein. To avoid incorrectly folded protein due to wrong disulfide (S-S) linking, cysteines 89 and 186 have been mutated to alanines in this enzyme. Alanine mutations or GST fusion does not alter the activity of the enzyme compared to wild-type.4,5WARNING This product is not for human or veterinary use.