2-Chloro-1,4-dimethoxybenzene cation radical: Formation and role in the lignin peroxidase oxidation of anisyl alcohol

2-Chloro-1,4-dimethoxybenzene (2Cl-1,4-DMB) oxidation by lignin peroxidase (LiP) proceeds via the formation of the 2Cl-1,4-DMB cation radical as indic ated by ESR and UV/vis spectroscopy. The products of the LiP-catalyzed oxid ation of 2Cl-1,4-DMB were identified as 2-chloro-1,4-benzoquinone and the d imers dichlorotetramethoxybiphenyl and chloro(chlorodimethoxyphenyl)benzoqu inone. The addition of anisyl alcohol (AA) rapidly quenched the 2Cl-1,4-DMB cation radical optical absorption bands, suggesting that the cation radica l directly mediates the oxidation of AA. When LiP reactions are conducted i n the presence of 50 mu M 2Cl-1,4-DMB, the enzyme is inactivated; ho Never, this inactivation can be prevented by the addition of AA. This also sugges ts that the 2Cl-1,4-DMB cation radical formed in the reaction, in turn, oxi dizes AA. (C) 1998 Academic Press.