Arginine 132 (R132) mutations to histidine or cysteine frequently occur to cytosolic NADP+-isocitrate dehydrogenase (IDH1) in glioblastoma multiforme (GBM) patients. Mutant enzymes lose the normal IDH activity, but acquire an neomorphic ability to reduce α-KG to 2-hydroxyglutarate (2-HG), accompanied by the oxidation of NADPH. To examine whether the analogous mutation could cause similar effects in prokaryotic IDH, point mutations, Arg to His or Cys, were employed to homologous Arg153 of the NADP+-IDH from Escherichia coli (EcIDH), generating two mutants: EcIDH R153H and EcIDH R153C.