Catalyzes the reversible oxidation of malate to oxaloacetate. Exhibits remarkably higher catalytic efficiency for oxaloacetate reduction than for malate oxidation in vitro. Shows a high specificity for NAD(H), being almost inactive with NADP(H). (S)-malate + NAD(+) = H(+) + NADH + oxaloacetate Activity is inhibited by Zn(2+) and Co(2+). No activity in the presence of Fe(2+). kcat is 1870 sec(-1) with oxaloacetate as substrate. kcat is 542 sec(-1) with NADH as substrate. kcat is 4.71 sec(-1) with L-malate as substrate. kcat is 3.66 sec(-1) with NAD(+) as substrate. Optimum pH is 6.8 at 50 degrees Celsius and 8.5 at 30 degrees Celsius. Optimum temperature is 50 degrees Celsius. Homodimer. Belongs to the LDH/MDH superfamily. MDH type 2 family.