Catalyzes the reversible oxidation of malate to oxaloacetate. Can also oxidize tartrate. Can utilize both NAD and NADP. Catalytic efficiency for malate oxidation is 3-fold higher with NADP. (S)-malate + NADP(+) = H(+) + NADPH + oxaloacetate (S)-malate + NAD(+) = H(+) + NADH + oxaloacetate kcat is 2.6 sec(-1) for NAD-dependent malate oxidation. kcat is 1.4 sec(-1) for NADP-dependent malate oxidation. Optimum pH is 11 for malate oxidation. Optimum temperature is 95 degrees Celsius. Homotetramer. Ala at position 30 is responsible for coenzyme specificity. Asp or Glu is present at this position in most NAD-specific enzymes. The next residue, Arg, is important for NADP binding. Belongs to the LDH/MDH superfamily.