May supply 2-oxoglutarate for amino acid biosynthesis and ammonia assimilation via the glutamine synthetase/glutamate synthase (GS/GOGAT) pathway. D-threo-isocitrate + NADP(+) = 2-oxoglutarate + CO2 + NADPH Binds 1 Mg(2+) or Mn(2+) ion per subunit. Heterodimer. Leaves, nodules and roots with the relative amount of 1:3.4:7.7. Belongs to the isocitrate and isopropylmalate dehydrogenases family. Extended N-terminus.