Plays a role in intermediary metabolism and energy production (PubMed:8867815). It may tightly associate or interact with the pyruvate dehydrogenase complex (PubMed:8867815). D-threo-isocitrate + NADP(+) = 2-oxoglutarate + CO2 + NADPH Binds 1 Mg(2+) or Mn(2+) ion per subunit. Homodimer. Predominantly expressed in heart, liver and kidney (PubMed:8867815, PubMed:11278619). Expressed in activated B lymphocytes (PubMed:8867815). Up-regulated in activated B lymphocytes. By oxidative stress (at protein level). Acetylation at Lys-413 dramatically reduces catalytic activity. Deacetylated by SIRT3 (By similarity). Belongs to the isocitrate and isopropylmalate dehydrogenases family.