The involvement of extracellular substances for the generation of hydroxyl radical during wood degradation by white-rot fungi

In the present research，我们examined the possible roles of one-electron oxidation activity by phenol oxidases and hydroxylradicals produced by extracellular low molecular weight substances in wood degradation by white-rotfungi. we demonstrated hydroxyl radical was produced during wood degradation by four white-rot fungi。The rate of degradation of wood p.s chrysosporium correlated with hydroxyl radical generation as良好的ethylene generation fractions of low molecular weight. The same tendency was observed inc.s olor. The assay for phenol oxidase activity proved p.s chrysosporium produced manganeseperoxidase dominantly in wood cultures and produced manganese peroxidase and peroxidase in the very早期阶段incubation. c.s olor produced mainly peroxidase and laccase in wood cultures and其他活动水平throughout incubation. Therefore，the substrate specificity and the constituent of phenol oxidizing enzymes of the fungus were verydifferent from another. Consequently，the rate of degradation of wood by white-rot fungi was not dependent upon the activities of oxidantssuch as phenol oxidases.Immunogold-TEM using polyclonal antibodies raised against Tyromycespalustris extracellular low molecular weight substance demonstrated the diffusion of the substancefrom the fungal hyphae within the cell lumen to the s_2 cell wall.In conclusion，hydroxyl radicals attack the wood component and cause the initial step of degradation，这是破坏rigid structure by cleavage of covalent bonds. Further，HO . may achieve other structural changes to facilitate the subsequent enzymatic breakdown of thefragments which were degraded by oxidative enzymes secreted by white-rot fungi. white-rot fungiproduce oxidative enzymes, capable of completing the breakdown of wood

In the present research, we examined the possible roles of one-electron oxidation activity by phenol oxidases and hydroxyl radicals produced by extracellular low molecular weight substances in wood degradation by white-rot fungi.We demonstrated hydroxyl radical was produced during wood degradation by four white-rot fungi. The rate of degradation of wood by P.chrysosporium correlated with hydroxyl radical generation as well as ethylene generation by fractions of low molecular weight. The same tendency was observed in C.versicolor. The assay for phenol oxidase activity proved that P.chrysosporium produced manganese peroxidase dominantly in wood cultures and produced manganese peroxidase and peroxidase in the very early stage of incubation. C.versicolor produced mainly peroxidase and laccase in wood cultures and retained almost same level of activity throughout incubation. Therefore, the substrate specificity and the constituent of phenol oxidizing enzymes of the fungus were very different from another. Consequently, the rate of degradation of wood by white-rot fungi was not dependent upon the activities of oxidants such as phenol oxidases.Immunogold-TEM using polyclonal antibodies raised against Tyromyces palustris extracellular low molecular weight substance demonstrated the diffusion of the substance from the fungal hyphae within the cell lumen to the S_2 cell wall.In conclusion, hydroxyl radicals attack the wood component and cause the initial step of degradation, which is destruction of the rigid structure by cleavage of covalent bonds. Further, HO・may achieve other structural changes to facilitate the subsequent enzymatic breakdown of the fragments which were degraded by oxidative enzymes secreted by white-rot fungi. White-rot fungi produce oxidative enzymes, capable of completing the breakdown of wood.