Reaction catalyzed by 3alpha-hydroxysteroid 3-dehydrogenase (Si-specific) (1.1.1.50)
+
NADPH
+
H*
=
+
+
NADP+
5alpha-dihydroprogesterone
+
NADPH
+
H*
=
3alpha,5alpha-3-hydroxypregnan-20-one
+
5alpha,20alpha-tetrahydroprogesterone
+
NADP+
