TSTA3 is a NADP(H)-binding protein. It catalyzes the two-step epimerase and the reductase reactions in GDP-D-mannose metabolism, converting GDP-4-keto-6-D-deoxymannose to GDP-L-fucose. GDP-L-fucose is the substrate of several fucosyltransferases involved in the expression of many glycoconjugates, including blood group ABH antigens and developmental adhesion antigens. Mutations in this gene may cause leukocyte adhesion deficiency, type II. Recombinant human TSTA3 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.