The Isocitrate dehydrogenase cytoplasmic enzyme is a homodimer of 416 residues that belongs to the isocitrate and isopropylmalate dehydrogenases family. IDHC catalyzes the third step of the citric acid cycle, which involves the oxidative decarboxylation of isocitrate, forming ?ketoglutarate and CO2 in a two step reaction. The first step involves the oxidation of isocitrate to the intermediate oxalosuccinate, while the second step involves the production of ?ketoglutarate. During this process, either NADH or NADPH is produced along with CO2. Ca2+ can bind to IDHC as a complex with isocitrate, acting as a competitive inhibitor of Mg2+. The IDHC enzyme is inactivated by phosphorylation at Ser-113 and contains a clasp-like domain wherein both polypeptide chains in the dimer interlock. IDHC is expressed in a wide range of species and also in organisms that lack a complete citric acid cycle.
