D-threo-isocitrate + NADP(+) = 2-oxoglutarate + CO2 + NADPH Binds 1 Mg(2+) or Mn(2+) ion per subunit. Inhibition of this enzyme by phosphorylation regulates the branch point between the Krebs cycle and the glyoxylate bypass, which is an alternate route that accumulates carbon for biosynthesis when acetate is the sole carbon source for growth. Homodimer. Belongs to the isocitrate and isopropylmalate dehydrogenases family.