The role of CuCu dinuclear complexes in the oxidation of ascorbic acid by O2 a model for copper-oxidase activity

The copper(II) catalysed oxidation of ascorbate by molecular oxygen has been re-investigated. The kinetics require that electron transfer from a dinuclear copper-ascorbate complex to dioxygen be invoked as the initial step in the mechanism in nitrate, fluoride and chloride media, the reaction thus being presumed to go through a higher, rather than a lower, oxidation state intermediate. The catalytic mechanism of copper-oxidases is discussed in terms of this ‘model’ system, the former also containing CuCu dinuclear units as oxygen binding sites.