Has multiple catalytic activities. Apart from catalyzing the oxidation of (+)-tartrate to oxaloglycolate, also converts meso-tartrate to D-glycerate and catalyzes the oxidative decarboxylation of D-malate to pyruvate. NAD(+) + tartrate = 2-hydroxy-3-oxosuccinate + H(+) + NADH (2R,3S)-tartrate + NAD(+) = 2-hydroxy-3-oxosuccinate + H(+) + NADH (2R,3R)-tartrate + NAD(+) = 2-hydroxy-3-oxosuccinate + H(+) + NADH (2R,3R)-tartrate + H(+) = (R)-glycerate + CO2 (R)-malate + NAD(+) = CO2 + NADH + pyruvate Binds 1 Mg(2+) or Mn(2+) ion per subunit. Thermostable. Fully active after heating 10 min at 65 degrees Celsius and retains half its catalytic activity after 10 min at 72 degrees Celsius. Inactive after heating 10 min at 78 degrees Celsius. Carbohydrate acid metabolism; tartrate degradation; 2-hydroxy-3-oxosuccinate from L-tartrate: step 1/1. Carbohydrate acid metabolism; tartrate degradation; 2-hydroxy-3-oxosuccinate from meso-tartrate: step 1/1. Carbohydrate acid metabolism; tartrate degradation; D-glycerate from L-tartrate: step 1/1. Homodimer. Belongs to the isocitrate and isopropylmalate dehydrogenases family.