Isocitrate dehydrogenase (IDH=EC:188.8.131.52) is an enzyme that converts isocitrate to alpha-ketoglutarate ( -KG) and carbondioxide(CO2). There are three isozymes of IDH (IDH1, IDH2 and IDH3), the IDH1 and IDH2 are NADP-dependent and the IDH3 utilize NAD as cofactor. NAD-dependent IDH3 is located in mitochondria and is well known for its central role for energy production in the Krebs cycle. NADP-dependent IDHs (EC 184.108.40.206) are primarily located either in cytoplasm (IDH1) or mitochondria(IDH2). Both IDH1 and IDH2 play important roles in a number of cellular metabolic functions, including glucose sensing, glutamine metabolism, lipogenesis, and regulation of cellular redox status.
IDH activity significantly increases in human serum in parenchymal diseases of liver . Although activity of mutant IDH is elevatedin cancers like glioblastomas(GBM) , acute myeloid leukemia(AML) , intrahepatic cholangiocarcinoma_; particularly in the early phases of cancer, an increase is also observed in normal ype of IDH enzyme activity.