S-(hydroxymethyl)glutathione dehydrogenase (NADP+) activity
s-(hydroxymethyl)glutathione dehydrogenase (nadp+) activity
S-(hydroxymethyl)glutathione + NADP(+) = S-formylglutathione + NADPH + H(+)
s-(hydroxymethyl)glutathione + nadp(+) = s-formylglutathione + nadph + h(+)