title: Pathways for extracellular Fenton chemistry in the brown rot basidiomycete Gloeophyllum trabeum.
abstract: The brown rot fungus Gloeophyllum trabeum uses an extracellular hydroquinone-quinone redox cycle to reduce Fe(3+) and produce H(2)O(2). These reactions generate extracellular Fenton reagent, which enables G. trabeum to degrade a wide variety of organic compounds. We found that G. trabeum secreted two quinones, 2,5-dimethoxy-1,4-benzoquinone (2,5-DMBQ) and 4,5-dimethoxy-1,2-benzoquinone (4,5-DMBQ), that underwent iron-dependent redox cycling. Experiments that monitored the iron- and quinone-dependent cleavage of polyethylene glycol by G. trabeum showed that 2,5-DMBQ was more effective than 4,5-DMBQ in supporting extracellular Fenton chemistry. Two factors contributed to this result. First, G. trabeum reduced 2,5-DMBQ to 2,5-dimethoxyhydroquinone (2,5-DMHQ) much more rapidly than it reduced 4,5-DMBQ to 4,5-dimethoxycatechol (4,5-DMC). Second, although both hydroquinones reduced ferric oxalate complexes, the predominant form of Fe(3+) in G. trabeum cultures, the 2,5-DMHQ-dependent reaction reduced O(2) more rapidly than the 4,5-DMC-dependent reaction. Nevertheless, both hydroquinones probably contribute to the extracellular Fenton chemistry of G. trabeum, because 2,5-DMHQ by itself is an efficient reductant of 4,5-DMBQ.
authors.affiliation: Institute for Microbial and Biochemical Technology, U.S. Department of Agriculture Forest Products Laboratory, Madison, Wisconsin 53705, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Jensen
authors.forename: C J
authors.initials: CJ
authors.lastname: Houtman
authors.forename: Z C
authors.initials: ZC
authors.lastname: Ryan
authors.forename: K E
authors.initials: KE
authors.lastname: Hammel
mesh_terms: D016227:Benzoquinones / Q000378:metabolism; D002396:Catechols / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006873:Hydroquinones / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents; D008956:Models, Chemical; D010070:Oxalates / Q000378:metabolism; D010084:Oxidation-Reduction; D011124:Polyporaceae / Q000378:metabolism*; D014934:Wood
chemical_list: D016227:Benzoquinones; D002396:Catechols; C045076:Fenton's reagent; D005290:Ferric Compounds; D006873:Hydroquinones; D007502:Iron Chelating Agents; D010070:Oxalates; D006861:Hydrogen Peroxide; D007501:Iron