Oxidation of methoxybenzenes by manganese peroxidase and by Mn3+.
Manganese peroxidase, produced by some white-rot fungi during lignin degradation, catalyzes the oxidation of Mn2+ to Mn3+. Whereas Mn3+ is known to oxidize phenolic compounds, its role in lignin degradation is not clear. We have used a series of methoxybenzenes with E1/2 values of 1.76-0.81 V (vs saturated calomel electrode) to investigate the oxidizing ability of Mn3+ chelates generated chemically and enzymatically. Although lignin peroxidase has been shown to oxidize high potential congeners, our results show that manganese peroxidase, or physiological concentrations of Mn3+, oxidize only the lower potential congeners. In addition, Mn3+ increased the rate of decay of the cation radical of 1,2,4,5-tetramethoxybenzene. The kinetics of decay continued to be first order, so Mn3+ does not oxidize the cation radical itself, but probably oxidizes a neutral dienyl radical derived from the cation radical. This indicates a possible role for Mn3+ in lignin degradation, as neutral dienyl radicals are proposed to be products of lignin peroxidase action.
Popp
J L
JL
Institute for Microbial and Biochemical Technology, USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin 53705-2398.
Kirk
T K
TK
D000840:Anisoles / Q000378:metabolism*; D001487:Basidiomycota / Q000201:enzymology; D001673:Biodegradation, Environmental; D007700:Kinetics; D008031:Lignin / Q000378:metabolism; D008345:Manganese / Q000378:metabolism / Q000494:pharmacology; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*
D000840:Anisoles; D008345:Manganese; D008031:Lignin; C060998:anisole; D010544:Peroxidases; C042858:lignin peroxidase; C051129:manganese peroxidase