(S)-lactate + NAD(+) = H(+) + NADH + pyruvate Fermentation; pyruvate fermentation to lactate; (S)-lactate from pyruvate: step 1/1. Homotetramer. Belongs to the LDH/MDH superfamily. LDH family. Was originally (Ref.1) thought to be a malate dehydrogenase or an NADH-dependent acyl-CoA reductase.