(2R)-hydroxybutanoate + FAD + H(+) <=> 2-oxobutanoate + FADH2
(2r)-hydroxybutanoate + fad + h(+) <=> 2-oxobutanoate + fadh2
(2R)-hydroxybutanoate + FAD + H(+) <=> 2-oxobutanoate + FADH2
(2r)-hydroxybutanoate + fad + h(+) <=> 2-oxobutanoate + fadh2