<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 [<cite idref="PUB00004691"/>, <cite idref="PUB00003276"/>, <cite idref="PUB00005036"/>, <cite idref="PUB00000160"/>]. The signature pattern of this entry is located in a conserved region, which contains a glycine-rich stretch of residues located in the C-terminal section.</p> Isocitrate/isopropylmalate dehydrogenase, conserved site