Mitochondrial isocitrate dehydrogenase catalyzes the reaction of isocitrate and NAD+ to form 2-oxoglutarate, CO2 and NADH + H+. The enzyme is a complex of regulatory and catalytic subunits, and has been characterized experimentally in rice as a component of the process by which inorganic nitrogen is assimilated and used for amino acid biosynthesis in root cells (Akibo et al. 2005).