Catalyzes the conversion of lactate to pyruvate. (S)-lactate + NAD(+) = H(+) + NADH + pyruvate Allosterically activated by fructose 1,6-bisphosphate (FBP). It binds two fructose 1,6-bisphosphate (FBP) molecules per tetramer. kcat is 745 sec(-1) for pyruvate (in the presence of fructose 1,6-bisphosphate (FBP)). kcat is 131 sec(-1) for pyruvate (in the absence of fructose 1,6-bisphosphate (FBP)). Fermentation; pyruvate fermentation to lactate; (S)-lactate from pyruvate: step 1/1. Homotetramer. Belongs to the LDH/MDH superfamily. LDH family.