CONVERSION OF LIGNIN PEROXIDASE COMPOUND-III TO ACTIVE ENZYME BY CATION RADICALS

It has been previously reported that the catalytically inactive compou nd III form of lignin peroxidase is formed during the oxidation of cer tain chemicals such as phenols (P. J. Harvey and J. M. Palmer, 1990, J . Biotechnol. 13, 169-179). Here me provide evidence that the cation r adicals of methoxybenzenes such as 1,2,4,5-tetramethoxybenzene (TRIP) and veratryl alcohol promote the oxidative conversion of compound III back to ferric enzyme. Two kinetic phases were observed during the oxi dation of TMB by lignin peroxidase. In the first phase the formation o f TMB cation radical and compound III were observed simultaneously. Th e second phase involved a rapid disappearance of compound III and the TRIP cation radical. Ferric enzyme appeared concomitantly with the dis appearance of compound III. The TMB cation radical, generated electroc hemically, was able to convert compound III to ferric enzyme. Comparat ive studies using veratryl alcohol were performed and supported the id ea that the cation radical of these chemicals are capable of reactivat ing compound III. The significance of these reactions with respect to lignin peroxidase catalysis are discussed. (C) 1994 Academic Press, In c.