QDPR is a member of the short-chain dehydrogenases/reductase (SDR) family of enzymes. Functioning as a homodimer, QDPR plays an important role in the recycling of tetrahydrobiopterin (BH4), an essential cofactor for the hydroxylation of the aromatic amino acids (tryptophan, tyrosine and phenylalanine). More specifically, QDPR catalyzes the regeneration of BH4 from quinonoid dihydrobiopterin (qBH2), the product generated from the hydroxylation reactions. Mutations in the gene encoding QDPR can lead to phenylketonuria II. Recombinant human QDPR protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques. MW: 28.2 kDa (267 aa, 1-244 aa + His Tag). Purity ≥90%