Carbon dioxide mediates Mn(II)-catalyzed decomposition of hydrogen peroxide and peroxidation reactions.

Mn(II) can catalyze the decomposition of H(2)O(2) and, in the presence of H(2)O(2), can catalyze the oxidation of NADH. Strikingly, these processes depend on the simultaneous presence of both CO(2) and HCO(3)(-). This explains the exponential dependence of the rates on [HCO(3)(-)], previously noted by other workers. These processes are inhibited by Mn-superoxide dismutase, establishing the generation of O(2)(-) and its role as an essential reactant. A scheme of reactions, consistent with the known properties of this system, is proposed. The large rate enhancements provided by HCO(3)(-) + CO(2), and the abundance of both of these species in vivo, suggest that similar reactions have relevance to the oxidative stress imposed by O(2)(-) and H(2)O(2).