Only C-2 specific glucose oxidase activity is expressed in ligninolytic cultures of the white rot fungus Phanerochaete c
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© Springer-Verlag 1996
S H O RT C O M M U N I C AT I O N
Jindřich Volc · Elena Kubátová · Geoffrey Daniel · Věra Přikrylová
Only C-2 specific glucose oxidase activity is expressed in ligninolytic cultures of the white rot fungus Phanerochaete chrysosporium Received: 23 February 1996 / Accepted: 6 March 1996
Abstract Two D-glucose-oxidizing enzymes, glucose 1-oxidase (G1O) and pyranose 2-oxidase (P2O, glucose 2-oxidase), have been proposed to play an important role in the ligninolytic system of the white rot fungus Phanerochaete chrysosporium by producing hydrogen peroxide. The possible simultaneous expression and metabolic cooperation of the two oxidases was studied in strains ME-446 (reported as G1O positive) and K-3 (P2O positive) grown in liquid media and under near natural conditions on birch wood blocks. The presence of G1O and P2O in extracts from mycelia and decayed wood was determined by chromatographic, electrophoretic, and immunological methods. Attempts to separate these enzymes and to detect G1O and its reaction product, D-glucono-1,5-lactone, failed. Evidence was obtained only for P2O expression in both strains. Accordingly, P2O, rather than G1O, represents a major source of sugar-derived H2O2 under the culture conditions used. Key words Glucose 1-oxidase · Pyranose 2-oxidase · Hydrogen peroxide · 2-Keto-D-glucose · Phanerochaete chrysosporium Abbreviations G1O Glucose 1-oxidase · P2O Pyranose 2-oxidase · TBS Tris-buffered saline
Introduction An important component of the unique ligninolytic systems evolved by white rot fungi is the source of H2O2 re-
J. Volc (Y) · E. Kubátová · V. Přikrylová Institute of Microbiology, Academy of Sciences of the Czech Republic, Vídeňská 1083, 14220 Prague 4, Czech Republic Tel. +42-2475298; Fax +42-24752384 e-mail: [email protected] G. Daniel Department of Forest Products, The Swedish University of Agricultural Sciences, S-75007 Uppsala, Sweden
quired for reactions catalyzed by lignin-depolymerizing peroxidases. Several oxidases are proposed to play a role in supplying H2O2 in the system employed by the most studied representative of these fungi, the basidiomycete Phanerochaete chrysosporium. These include glyoxal oxidase (Kersten and Kirk 1987), methanol oxidase (Eriksson and Nishida 1988), glucose 1-oxidase (G1O; EC 1.1.3.4; Kelley and Reddy 1986), pyranose 2-oxidase (P2O; EC 1.1.3.10; Volc and Eriksson 1988); which acts on several monosaccharides in the pyranose form, and cellobiose oxidase/dehydrogenase (Kremer and Wood 1992). Recently, we have shown that there are high activities of P2O produced by P. chrysosporium and other white rot fungi in birch wood decayed under near natural conditions (Daniel et al. 1994). Based on the known substrate specificities of P2O and G1O, a scheme for more efficient production of H2O2 can be postulated in which the primary products of the two enzymes, 2-keto-D-glucose (Janssen and Ruelius 1968) and D-glucono-1,5-lactone (Geigert et al. 1983), are subsequently oxidized to 2-keto-D-gluconate (Fig. 1), thus producing 2 mol H2O2
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