Catalyzes the reversible conversion of (S)-malate to oxaloacetate in the cytoplasm where oxaloacetate is used for gluconeogenesis. (S)-malate + NAD(+) = H(+) + NADH + oxaloacetate kcat is 350 sec(-1) with NADH as substrate (at 24 degrees Celsius and pH 7.5). Optimum temperature is 40 degrees Celsius. Homodimer. Belongs to the LDH/MDH superfamily. MDH type 2 family.