Reaction catalyzed by sepiapterin reductase (L-erythro-7,8-dihydrobiopterin forming) (1.1.1.153), sepiapterin reductase (L-threo-7,8-dihydrobiopterin forming) (1.1.1.325)
+
NADPH
+
=
+
NADP+
sepiapterin
+
NADPH
+
H+
=
tetrahydrobiopterin
+
NADP+
