IDH1 and cancer: Mutations in either IDH1 or IDH 2 (found in several types of cancers, including gliomas [23,24,25,26]) result in not only loss of normal enzyme function (i.e., catalysis of the oxidative decarboxylation of isocitrate with concomitant production of NADH), but also to a pathological gain of a new enzyme function (i.e., reduction of 2-OG to the oncometabolite d-2-HG, while consuming NADH).