title: Mineralization of aromatic compounds by brown-rot basidiomycetes - mechanisms involved in initial attack on the aromatic ring.
abstract: Benzaldehyde and its metabolic intermediates were effectively degraded by the brown-rot basidiomycetes Tyromyces palustris and Gloeophyllum trabeum. The pathway of benzaldehyde degradation was elucidated by the identification of fungal metabolites produced upon the addition of benzaldehyde and its metabolic intermediates. The oxidation and reduction occurred simultaneously, forming benzyl alcohol and benzoic acid as major products. Hydroxylation reactions, which seemed to be a key step, occurred on benzaldehyde and benzoic acid, but not on benzyl alcohol, to form corresponding 4-hydroxyl and 3,4-dihydroxyl derivatives. 1-Formyl derivatives were oxidized to 1-carboxyl derivatives at several metabolic stages. All of these reactions resulted in the formation of 3,4-dihydroxybenzoic acid. This was further metabolized via the decarboxylation reaction to yield 1,2,4-trihydroxybenzene, which may be susceptible to the ring-fission reaction. Ring-U-14C-labelled benzaldehyde and benzoic acid were effectively mineralized, clearly indicating that the brown-rot basidiomycetes are capable of metabolizing certain aromatic compounds to CO2 and H2O, despite the fact that brown-rot fungi cannot degrade polymeric lignin. Inhibitor experiments, using hydroxyl radical scavengers, catalase and cytochrome P450 inhibitors, strongly suggested that the aromatic hydroxylation reactions found in the brown-rot fungi are catalysed by intracellular enzyme(s), but not by Fenton-reaction-derived hydroxyl radicals.
authors.affiliation: Faculty of Agriculture, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan1.
authors.forename: Fumika
authors.initials: F
authors.lastname: Kamada
authors.affiliation: Faculty of Agriculture, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan1.
authors.forename: Suzuna
authors.initials: S
authors.lastname: Abe
authors.affiliation: Faculty of Agriculture, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan1.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Hiratsuka
authors.affiliation: Faculty of Agriculture, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan1.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Wariishi
authors.affiliation: Faculty of Agriculture, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan1.
authors.forename: Hiroo
authors.initials: H
authors.lastname: Tanaka
mesh_terms: D001487:Basidiomycota / Q000378:metabolism*; D001547:Benzaldehydes / Q000737:chemistry / Q000378:metabolism; D019817:Benzoic Acid / Q000737:chemistry / Q000378:metabolism; D001592:Benzyl Alcohols / Q000737:chemistry / Q000378:metabolism; D002374:Catalase / Q000037:antagonists & inhibitors / Q000378:metabolism; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D006841:Hydrocarbons, Aromatic / Q000737:chemistry* / Q000378:metabolism*; D017665:Hydroxyl Radical / Q000378:metabolism
chemical_list: D001547:Benzaldehydes; D001592:Benzyl Alcohols; D065607:Cytochrome P-450 Enzyme Inhibitors; D006841:Hydrocarbons, Aromatic; D017665:Hydroxyl Radical; D019817:Benzoic Acid; D003577:Cytochrome P-450 Enzyme System; D002374:Catalase; C032175:benzaldehyde