OXIDATIVE DECOMPOSITION OF MALONIC-ACID AS BASIS FOR THE ACTION OF MANGANESE PEROXIDASE IN THE ABSENCE OF HYDROGEN-PEROXIDE

Manganese peroxidase (MnP) from the ligninolytic basidiomycetes Phlebi a radiata and Nematoloma frowardii was found to decompose malonate oxi datively in the absence of H2O2 in a reaction system consisting of the enzyme, sodium malonate and MnCl2, The enzymatic oxidation resulted i n a substantial decrease in malonate concentration and the formation o f CO2, oxalate, glyoxylate and formate, Simultaneously with the decomp osition of malonate, Mn(II) was oxidized to Mn(III) leading to high tr ansient concentrations of the latter. MnP action in the absence of H2O 2 started slowly after a lag period of 3 h, The lag period was conside rably shortened after a single addition of Mn(III). Superoxide dismuta se and catalase inhibited the enzymatic reaction partly, ascorbate com pletely. ESR studies demonstrated the formation of a carbon-centered r adical during the course of the reaction. We propose that the latter g enerates peroxides that can be used by MnP to oxidize Mn(II) to Mn(III ), (C) 1998 Federation of European Biochemical Societies.