(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(+)