Peroxyl radicals are potential agents of lignin biodegradation

Abstract

Past work has shown that the extracellular manganese- dependent peroxidases (MnPs) of ligninolytic fungi degrade the principal non-phenolic structures of lignin when they peroxidize unsaturated fatty acids. This reaction is likely to be relevant to ligninolysis in sound wood, where enzymes cannot penetrate, only if it employs a small, diffusible lipid radical as the proximal oxidant of lignin. Here we show that a non-phenolic b- O-4-linked lignin model dimer was oxidized to products indicative of hydrogen abstraction and electron transfer by three different peroxyl radical-generating systems: (a) MnP/Mn(II)/ linoleic acid, (b) arachidonic acid in which peroxidation was initiated by a small amount of H2O2/Fe(II), and (c) the thermolysis in air of either 4, 4`-azobis(4-cyanovaleric acid) or 2,2`-azobis(2-methylpropionamidine) dihydrochloride. Some quantitative differences in the product distributions were found, but these were attributable to the presence of electron-withdrawing substituents on the peroxyl radicals derived from azo precursors. Our results introduce a new hypothesis: that biogenic peroxyl radicals may be agents of lignin biodegradation.

Citation

Kapich, Alexander N.; Jensen, Kenneth A.; Hammel, Kenneth E. 1999. Peroxyl radicals are potential agents of lignin biodegradation. FEBS letters. No. 461 (1999).:p. 115-119 : ill.