CREATION OF METAL-COMPLEXING AGENTS, REDUCTION OF MANGANESE-DIOXIDE, AND PROMOTION OF MANGANESE PEROXIDASE-MEDIATED MN(III) PRODUCTION BY CELLOBIOSE - QUINONE OXIDOREDUCTASE FROM TRAMETES-VERSICOLOR

Culture supernatants of the white-rot fungus Trametes versicolor were found to contain Mn(III)-complexing agents able to effectively promote manganese-dependent peroxidase (MnP)-mediated oxidation of phenol red . The high molecular weight fractions of these supernatants contained carbohydrate polymers that functioned as effective Mn(III)-complexing agents. Gluconic and glucuronic acids were also found to be effective Mn(III)-complexing ligands capable of supporting MnP-mediated phenol r ed oxidation, as was the cellobionic acid formed from cellobiose by ce llobiose:quinope oxidoreductase (CBQase) (EC 1.1.5.1). The formation o f cellulose-derived sugar acid manganese-complexing agents by CBQase i ncreased in the presence of wood pulp and cellulolytic enzymes. CBQase , while oxidizing cellobiose, reduced insoluble Mn(IV)O-2 to Mn(II) or Mn(III) by a reaction whose rate is determined by the nature of the m anganese-complexing agents present. A model is proposed to explain how oxidation of carbohydrate and reduction of MnO2 and quinones by CBQas e may complement oxidation by MnP, thus promoting lignin biodegradatio n.