Dismutation of superoxide anions with a metal-based catalyzer (denoted by M) in a redox cycle. The Mn and Mn-1 show the oxidized and reduced forms of the metallic center, respectively. The metallic center is able to convert a superoxide anion to oxygen in the first half reaction by accepting an electron. In the second half reaction, the reduced metal atom donates the electron to another superoxide anion in order to form hydrogen peroxide, regenerating the metal ion in its original oxidation state.