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Description

Isocitrate dehydrogenase [NADP] (also known as IDH, ICDH) catalyzes the oxidative decarboxylation of isocitrate to alpha-ketoglutarate. 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 E.coli the activity of a NADP+-dependent ICDH is controlled by the phosphorylation of a serine residue and the phosphorylated form of ICDH is completely inactivated. It has been reported that if Ser113 is replaced by alanine, cysteine, threonine, or tyrosine there is some loss of enzymatic activity. However, substitution by aspartic acid completely abolishes its activity. ICDH contains three domains: a large alpha + beta domain, a small alpha/beta domain and an alpha/beta clasp-like domain involving both subunits. (Ref.: Hurley, JH et al (1989). Proc. Natl. Acad. Sci. USA. 86 (22), 8635-8639).