Isocitrate dehydrogenase [NADP], mitochondrial is an enzyme that in humans is encoded by the IDH2 gene. Isocitrate dehydrogenases are enzymes that catalyze the oxidative decarboxylation of isocitrate to 2-oxoglutarate. These enzymes belong to two distinct subclasses, one of which utilizes NAD(+) as the electron acceptor and the other NADP(+). Five isocitrate dehydrogenases have been reported: three NAD(+)-dependent isocitrate dehydrogenases, which localize to the mitochondrial matrix, and two NADP(+)-dependent isocitrate dehydrogenases, one of which is mitochondrial and the other predominantly cytosolic. Each NADP(+)-dependent isozyme is a homodimer. The protein encoded by the IDH2 gene is the NADP(+)-dependent isocitrate dehydrogenase found in the mitochondria. It plays a role in intermediary metabolism and energy production. This protein may tightly associate or interact with the pyruvate dehydrogenase complex. Somatic mosaic mutations of this gene have also been found associated to Ollier disease and Maffucci syndrome. Structure Isocitrate dehydrogenase is composed of 3 subunits, allosterically regulated, and requires an integrated Mg2+ or Mn2+ ion. The mitochondrial form of IDH, like most isoforms, is a homodimer, in which two identical monomer subunits form one unit. The structure of Mycobacterium tuberculosis IDH-1 bound with NADPH and Mn2+ has been solved by X-ray crystallography. It is a homodimer in which each subunit has a Rossmann fold, and a common top domain of interlocking β sheets. Mtb IDH-1 is most structurally similar to the R132H mutant human IDH found in certain glioblastomas. Similar to human R132H ICDH, Mtb ICDH-1 also catalyzes the formation of α-hydroxyglutarate. Function Isocitrate dehydrogenase is a digestive enzyme that is used in the citric acid cycle. Its main function is to catalyze the oxidative decarboxylation of isocitrate into alpha-ketoglutarate. Human isocitrate dehydrogenase regulation is not fully understood however, it is known that NADP and Ca2+ bind in the active site to create three different conformations. These conformations form in the active site and are as follows: a loop is form in the inactive enzyme, a partially unraveled alpha helix in the semi open form, and an alpha helix in the active form. Clinical significance The mitochondrial form of IDH2 is correlated with many diseases. Mutations in IDH2 are associated with 2-hydroxyglutaric aciduria, a condition that causes progressive damage to the brain. The major types of this disorder are called D-2-hydroxyglutaric aciduria (D-2-HGA), L-2-hydroxyglutaric aciduria (L-2-HGA), and combined D,L-2-hydroxyglutaric aciduria (D,L-2-HGA). The main features of D-2-HGA are delayed development, seizures, weak muscle tone (hypotonia), and abnormalities