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Carbohydrate oxidases in ericoid and ectomycorrhizal fungi: a possible source of Fenton radicals during the degradation of lignocellulose
Author(s) -
BURKE R. M.,
CAIRNEY J. W. G.
Publication year - 1998
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1046/j.1469-8137.1998.00235.x
Subject(s) - phanerochaete , cellobiose dehydrogenase , cellobiose , chrysosporium , botany , biology , chemistry , lignin , biochemistry , cellulose , cellulase
Isolates of the ericoid mycorrhizal fungus Hymenoscyphus ericae (Read) Korf et Kernan, and the ectomycorrhizal fungi Suillus variegatus (Swartz ex Fr.) and Pisolithus tinctorius (Pers.) Coker & Couch, along with a Cortinarius sp. and the white rot Phanerochaete chrysosporium Burdsall were examined for the ability to oxidize carbohydrates to their corresponding lactones and to excrete the H 2 O 2 produced thereby. All except Phanerochaete chrysosporium were found to express cellobiose oxidase (cellobiose dehydrogenase, EC 1.1.19.88) and glucose oxidase (β‐ d ‐glucose∶oxygen 1‐oxidoreductase, EC 1.1.3.4) when grown on cellobiose and glucose respectively. Production of extracellular H 2 O 2 was visualized during growth on both substrates using ABTS as the chromogen. According to the Fenton reaction, H 2 O 2 will react with hydrated or chelated Fe(II) in the environment to produce hydroxyl (Fenton) radicals, HO · . Mycelial extracts from each of the mycorrhizal fungi produced HO · in the presence of cellobiose and Fe(II), presumably mediated by H 2 O 2 produced by cellobiose oxidase activity in the extracts. Conditions favourable to HO · production were shown to exist in Modified Melin–Norkrans medium, and the data discussed in relation to previously observed lignin degradation by mycorrhizal fungi.