SOD2 and early-onset autosomal dominant Alzheimer disease: SOD2 neutralizes superoxide radical and is converted into hydrogen peroxide,26 controlling dioxygen toxicity in the mitochondria, an organelle of extreme oxidative load (Fig. 4).28,29 Mn is a highly studied transition metal, and significantly reduced levels of Mn have been measured in patients with Alzheimer’s disease and associated with mild cognitive impairment.30 There are other key enzymes than SOD2 dependent on Mn, such as glutamine synthetase, arginase and pyruvate carboxylase.31