InterPro

The isocitrate and isopropylmalate dehydrogenases family includes isocitrate dehydrogenase (IDH), 3-isopropylmalate dehydrogenase (IMDH) and tartrate dehydrogenase.

IDH is an important enzyme of carbohydrate metabolism which catalyses the oxidative decarboxylation of isocitrate into alpha-ketoglutarate [PMID: 2682654, PMID: 1939242]. IDH is either dependent on NAD⁺ (EC:1.1.1.41) or on NADP⁺ (EC: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 Escherichia coli, 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.

IMDH (EC:1.1.1.85) catalyses the third step in the biosynthesis of leucine in bacteria and fungi, the oxidative decarboxylation of 3-isopropylmalate into 2-oxo-4-methylvalerate [PMID: 1748999, PMID: 7773180].

Tartrate dehydrogenase (EC:1.1.1.93) shows strong homology to prokaryotic isopropylmalate dehydrogenases and, to a lesser extent, isocitrate dehydrogenase [PMID: 8053675]. It catalyses the reduction of tartrate to oxaloglycolate [PMID: 8053675].

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 [PMID: 9086278].