Isopropylmalate dehydrogenase-like domain <p>Isocitrate dehydrogenase (IDH) [<cite idref="PUB00004691"/>, <cite idref="PUB00002669"/>] is an important enzyme of carbohydrate metabolism which catalyses the oxidative decarboxylation of isocitrate into alpha-ketoglutarate. IDH is either dependent on NAD⁺ (<db_xref db="EC" dbkey="1.1.1.41"/>) or on NADP⁺ (<db_xref db="EC" dbkey="1.1.1.42"/>). In eukaryotes there are at least three isozymes of IDH: two are located in the mitochondrial matrix (one NAD⁺-dependent, the other NADP⁺-dependent), while the third one (also NADP⁺-dependent) is cytoplasmic. In <taxon tax_id="562">Escherichia coli</taxon> the activity of a NADP⁺-dependent form of the enzyme is controlled by the phosphorylation of a serine residue; the phosphorylated form of IDH is completely inactivated.</p><p>3-isopropylmalate dehydrogenase (<db_xref db="EC" dbkey="1.1.1.85"/>) (IMDH) [<cite idref="PUB00003276"/>, <cite idref="PUB00005036"/>] catalyses the third step in the biosynthesis of leucine in bacteria and fungi, the oxidative decarboxylation of 3-isopropylmalate into 2-oxo-4-methylvalerate. Tartrate dehydrogenase (<db_xref db="EC" dbkey="1.1.1.93"/>) [<cite idref="PUB00000160"/>] catalyses the reduction of tartrate to oxaloglycolate.</p><p>These enzymes are evolutionary related. To this family also belongs the enzyme tartrate dehydrogenase, which shows strong homology to prokaryotic isopropylmalate dehydrogenases and, to a lesser extent, isocitrate dehydrogenase [<cite idref="PUB00000160"/>].</p><p>This entry represents a structural domain found in all types of isocitrate dehydrogenase, and in isopropylmalate dehydrogenase and tartrate dehydrogenase. The crystal structure of Escherichia coli isopropylmalate dehydrogenase has been described [<cite idref="PUB00022856"/>]. </p>