In enzymology, (S,S)-butanediol dehydrogenase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are (S,S)-butane-2,3-diol and oxidised nicotinamide adenine dinucleotide (NAD). Its products are (S)-acetoin, reduced NADH, and a proton.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD or NADP as acceptor. The systematic name of this enzyme class is (S,S)-butane-2,3-diol:NAD oxidoreductase. Other names in common use include L-butanediol dehydrogenase, L-BDH, and L()-2,3-butanediol dehydrogenase (L-acetoin forming). This enzyme participates in butanoic acid metabolism.