Sepiapterin reductase (L-threo-7,8-dihydrobiopterin forming)

Sepiapterin reductase (L-threo-7,8-dihydrobiopterin forming) is an enzyme with systematic name L-threo-7,8-dihydrobiopterin:NADP+ oxidoreductase. This enzyme catalyses the following chemical reaction


 * (1) L-threo-7,8-dihydrobiopterin + NADP+ $$\rightleftharpoons$$ sepiapterin + NADPH + H+
 * (2) L-threo-tetrahydrobiopterin + 2 NADP+ $$\rightleftharpoons$$ 6-pyruvoyl-5,6,7,8-tetrahydropterin + 2 NADPH + 2 H+

This bacterial (Chlorobium tepidum) enzyme catalyses the final step in the de novo synthesis of tetrahydrobiopterin from GTP.