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