This entry represents the NAD-dependent malate dehydrogenase found in eukaryotes and certain gamma proteobacteria. The enzyme is involved in the citric acid cycle as well as the glyoxalate cycle. Several isoforms exist in eukaryotes. In Saccharomyces cereviseae, for example, there are cytoplasmic, mitochondrial and peroxisomal forms. Although malate dehydrogenases have in some cases been mistaken for lactate dehydrogenases due to the similarity of these two substrates and the apparent ease with which evolution can toggle these activities, critical residues have been identified [PMID:11021970] which can discriminate between the two activities.