Malic dehydrogenase (MDH) exists as two isoforms within eukaryotic cells, one that is expressed in the mitochondria and functions in the TCA cycle and one in the cytoplasm that converts malate from the mitochondria back into oxaloacetate.http://www.creative-enzymes.com/product/Native-Chicken-Malic-Dehydrogenase-oxalacetatedecarboxylating-_1292.html