Sepiapterin Reductase (SPR)

Sepiapterin reductase (7,8-dihydrobiopterin:NADP+ oxidoreductase; EC 1.1.1.153) catalyzes the NADPH-dependent reduction of various carbonyl substances, including derivatives of pteridines, and belongs to a group of enzymes called aldo-keto reductases. SPR plays an important role in the biosynthesis of tetrahydrobiopterin (BH4).

The clone encoded a protein of 261 amino acids with a calculated molecular mass of 28,047 Da. The predicted amino acid sequence of human sepiapterin reductase shows 74% identity with the rat enzyme and a striking homology with human carbonyl reductase, estradiol 17-beta-dehydrogenase, and 3-beta-hydroxy-5-ene steroid dehydrogenase, especially in the N-terminal region.