Degradation of chemicals by reactive radicals produced by cellobiose dehydrogenase from Phanerochaete chrysosporium

Abstract

Phanerochaete chrysosporium, grown on cellulose, produced a cellobiose-dependent dehydrogenase which reduced both ferric iron and molecular oxygen, resulting in the generation of the hydroxyl radical. The hydroxyl radical was detected in reaction mixtures with and without the addition of exogenous H2O2. The purified reductase and the fungus grown under nonligninolytic conditions that promote the production of the reductase were able to depolymerize an insoluble polyacrylate polymer. When oxalate, a secondary metabolite of P. chrysosporium, was used as the iron chelator, it was oxidized by the hydroxyl radical to form the carboxylate anion radical, a strong reductant. Under these reductive conditions, the enzyme was shown to catalyze the reduction of bromotrichloromethane to the trichloromethyl radical. We propose that these oxidative and reductive mechanisms may contribute to the degradation of a wide range of environmental pollutants by fungi which produce this enzyme.