(2R)-hydroxybutanoate + NADP(+) => 2-oxobutanoate + NADPH + H(+)
(2r)-hydroxybutanoate + nadp(+) => 2-oxobutanoate + nadph + h(+)
(2R)-hydroxybutanoate + NADP(+) => 2-oxobutanoate + NADPH + H(+)
(2r)-hydroxybutanoate + nadp(+) => 2-oxobutanoate + nadph + h(+)