D-threo-isocitrate + NADP(+) = 2-oxoglutarate + CO2 + NADPH Binds 1 Mg(2+) or Mn(2+) ion per subunit. Optimum pH is 8.6. Optimum temperature is 90 degrees Celsius. Thermostable. Homodimer. Belongs to the isocitrate and isopropylmalate dehydrogenases family.