Transformations of arylpropane lignin model compounds by a lignin peroxidase of the white-rot fungus Phanerochaete chrysosporium.
Various lignin model compounds of the O-arylpropane type were oxidized with purified lignin peroxidase from the white-rot fungus Phanerochaete chrysosporium, and oxidation products were identified by gas-chromatography/mass-spectroscopy procedures. Our results are in accord with the theory that lignin peroxidase catalyzes one-electron oxidations of its substrates with formation of cation radicals, and that these radicals undergo degradative reactions that are predictable from a knowledge of cation radical and oxygen chemistry. Cation radicals formed from O-arylpropane model compounds appeared to undergo the following types of degradative transformations: addition of water to ring-centered radicals, followed by proton loss yielding quinones and alcohols; nucleophilic attack by hydroxy functions on propanoid moieties giving cyclic ketals as intermediates which decompose to yield side chain migration products; transfer of the charge of a radical from a ring to the associated alkyl moiety through an ether bond, with loss of a proton from the latter, forming a new carbon-centered radical. The new alkyl-centered radicals apparently were able to abduct dioxygen to form peroxyl radicals which decomposed giving a variety of oxidation products and probably superoxide anion. Specific examples of the above transformations are presented, and their relevance to lignin degradation is discussed.
D001487:Basidiomycota / Q000201:enzymology*; D001711:Biotransformation; D004987:Ethers / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D008031:Lignin / Q000031:analogs & derivatives* / Q000378:metabolism; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010105:Oxygenases / Q000302:isolation & purification / Q000378:metabolism*; D010544:Peroxidases; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013379:Substrate Specificity
D004987:Ethers; D008031:Lignin; D010544:Peroxidases; C042858:lignin peroxidase; D010105:Oxygenases