label: (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin + NADP(+) = 6-lactoyl-5,6,7,8-tetrahydropterin + NADPH + H(+)
label_lc: (6r)-l-erythro-5,6,7,8-tetrahydrobiopterin + nadp(+) = 6-lactoyl-5,6,7,8-tetrahydropterin + nadph + h(+)