Oxidation of Cu(I)-Thionein by Enzymically Generated H2O2

Abstract

There is no evidence of an oxidative breakdown of Cu(I)-thionein leading to Cu(II). Thus it was of interest to use L- and D-amino acid oxidases, amine oxidase and galactose oxidase to control the oxidation of Cu(I)-thionein by enzymically generated H2O2. In the presence of these enzymes Cu(II) was generated in each case. In a more detailed study the Cu(I)-thiolate chromophores of Cu-thionein were oxidized in the presence of xanthine oxidase as deduced from spectrometrical measurements using EPR and circular dichroism. Unlike Cu2ZN2-superoxide dismutase catalase inhibited the oxidative cleavage, suggesting peroxide as the actual oxidizing agent. Possibly there is an enzymic oxidative pathway for the generation of biologically important Cu(II).