Catalyzes the conversion of lactate to pyruvate. (S)-lactate + NAD(+) = H(+) + NADH + pyruvate Under neutral conditions, the reaction is stimulated 4-fold by fructose 1,6-bisphosphate (FBP), however the L-lactate dehydrogenase is a nonallosteric enzyme. Calcium and zinc ions at 1 mM stimulate the activity almost 2-fold. Weakly inhibited by cadmium, cobalt and copper ions. kcat is 643 sec(-1) for pyruvate as substrate. Optimum pH is 5. Fermentation; pyruvate fermentation to lactate; (S)-lactate from pyruvate: step 1/1. Homotetramer. Belongs to the LDH/MDH superfamily. LDH family.