Background:  

    Isocitrate dehydrogenases 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 this

    gene is the NADP(+)-dependent isocitrate dehydrogenase found in the cytoplasm and peroxisomes. It contains the 

    PTS-1 peroxisomal targeting signal sequence. The presence of this enzyme in peroxisomes suggests roles in the

    regeneration of NADPH for intraperoxisomal reductions, such as the conversion of 2, 4-dienoyl-CoAs to 3-enoyl-CoAs,

    as well as in peroxisomal reactions that consume 2-oxoglutarate, namely the alpha-hydroxylation of phytanic acid. The

    cytoplasmic enzyme serves a significant role in cytoplasmic NADPH production. Alternatively spliced transcript variants 

    encoding the same protein have been found for this gene.