Plays a role in intermediary metabolism and energy production (PubMed:14512428). It may tightly associate or interact with the pyruvate dehydrogenase complex (PubMed:14512428). D-threo-isocitrate + NADP(+) = 2-oxoglutarate + CO2 + NADPH Binds 1 Mg(2+) or Mn(2+) ion per subunit. Homodimer. Acetylation at Lys-382 dramatically reduces catalytic activity. Deacetylated by SIRT3 (By similarity). Belongs to the isocitrate and isopropylmalate dehydrogenases family.