Catalyzes the conversion of lactate to pyruvate. It is stereospecific for L(+)-lactate. (S)-lactate + NAD(+) = H(+) + NADH + pyruvate Allosterically activated by fructose 1,6-bisphosphate (FBP). Inactivated by Mn(2+), Co(2+), Cd(2+) and Zn(2+). Optimum pH is 7. Long-term stability up to 80 degrees Celsius. Fructose 1,6-bisphosphate (FBP) increases the thermal stability at 90 degrees Celsius (pH 6.0). Fermentation; pyruvate fermentation to lactate; (S)-lactate from pyruvate: step 1/1. Homotetramer. Belongs to the LDH/MDH superfamily. LDH family.