Lignin Degradation by Phanerochaete chrysophorium: Biochemical Characterization of Extracellular Peroxidases

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The aim of the proposed project is to further our understanding of manganese peroxidase (MnP) and lignin peroxidase (LiP) from the lignin-degrading basidiomycete Phanerochaete chrysosporium. The underlying objectives of the proposed project are to further characterize the structure, mechanism and function of these enzymes and to clarify their role in lignin degradation. The binding, stoichiometry and mechanism of manganese oxidation by MnP will be studied by kinetic methods and by optical and NMR spectroscopy. Kinetic, spectroscopic and reactivity experiments also will be used to examine the mechanism of oxidation of syringyl and guaiacyl free phenolic dimeric model compounds by MnP and LiP from P. chrysosporium, and MnP and laccase form Dichomitus squalens. The mechanism of nonphenolic model compound degradation by D. squalens will also be examined. In addition, the mechanism of phenol oxidation by LiP and the mechanism of phenol inhibition of nonphenolic aromatic compound oxidation by LiP will be examined. Finally, using our P. chrysosporium DNA transformation system, a homologous expression system will be developed for these peroxidases. %%% Lignin is the second most abundant natural polymer in the biosphere and the most abundant renewable aromatic material. This research focusses on lignin degrading fungi and the structure and mechanisms of the enzymes responsible for catalyzing the degradation. The potential utilization of these micro organisms for transforming lignin into useful materials, chemicals and fuels is a very significant area of research.