Hydroxyl Radical Activity Associated with the Growth of White-Rot Fungi

Backa, Stefan; Gierer, Josef; Reitberger, Torbjörn; Nilsson, Thomas

doi:10.1515/hfsg.1993.47.3.181

Cited by 75 publications

(46 citation statements)

References 26 publications

(14 reference statements)

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“…Although the participation of hydroxyl radicals was long ago postulated in P. chrysosporium (Forney et al, 1982;Kutsuki & Gold, 1982;Bes et al, 1983;Kirk & Nakatsubo, 1983;Faison & Kirk, 1983;Evans et al, 1984), subsequent studies have shown that the attack of lignin model compounds by Fenton chemistry leads to products different from those detected in ligninolytic cultures or by isolated peroxidases (Kirk et al, 1985). Nevertheless, there is evidence that supports a role for Fenton chemistry in the degradation of lignocellulose by P. chrysosporium (Kremer & Wood, 1992a, b;Backa et al, 1993;Wood, 1994;Henriksson et al, 1995;Tanaka et al, 1999). It has been shown that cellobiose dehydrogenase (CDH), an oxidative enzyme secreted by both brown-and white-rot fungi, is capable of generating hydroxyl radicals by reducing Fe(III) and producing H 2 O 2 (Kremer & Wood, 1992a, b;Henriksson et al, 1995).…”

Section: Discussionmentioning

confidence: 97%

Cloning and characterization of the genes encoding the high-affinity iron-uptake protein complex Fet3/Ftr1 in the basidiomycete Phanerochaete chrysosporium

et al. 2007

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Section: Discussionmentioning

confidence: 97%

Cloning and characterization of the genes encoding the high-affinity iron-uptake protein complex Fet3/Ftr1 in the basidiomycete Phanerochaete chrysosporium

et al. 2007

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“…Further support for this hypothesis is that white rot fungi, which do not utilize the hydroxyl radical as the major oxidant (30,32), also produce oxalate (39,40,42,49). Despite reports on how the hydroxyl radical may be formed in white rot fungi (4,17,18), it is unlikely that oxalate would have a role in its formation. The chemical signatures of wood affected by white rot fungi and brown rot fungi are different (30).…”

Section: Discussionmentioning

confidence: 99%

“…The quinone undergoes cyclic oxidation-reduction reactions, serving as a shuttle for electrons from intracellular donors to extracellular acceptors. Although a similar mechanism has been proposed for white rot fungi (4,17,18) for hydroxyl radical formation, product analysis suggests that hydroxyl radical oxidation is relatively minor in comparison to peroxidase oxidation (30,32). The role of oxalate, ubiquitously found in brown rot fungi, as a chelating agent, and the role of pH, which is altered by the fungus, are not clear.…”

mentioning

confidence: 90%

Effect of pH and Oxalate on Hydroquinone-Derived Hydroxyl Radical Formation during Brown Rot Wood Degradation

Varela

Tien

2003

Appl Environ Microbiol

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The redox cycle of 2,5-dimethoxybenzoquinone (2,5-DMBQ) is proposed as a source of reducing equivalent for the regeneration of Fe 2؉ and H 2 O 2 in brown rot fungal decay of wood. Oxalate has also been proposed to be the physiological iron reductant. We characterized the effect of pH and oxalate on the 2,5-DMBQ-driven Fenton chemistry and on Fe 3؉ reduction and oxidation. Hydroxyl radical formation was assessed by lipid peroxidation. We found that hydroquinone (2,5-DMHQ) is very stable in the absence of iron at pH 2 to 4, the pH of degraded wood. . Catalase and hydroxyl radical scavengers were effective inhibitors of lipid peroxidation, whereas superoxide dismutase caused no inhibition. At a low concentration of oxalate (50 M), ferric ion reduction and lipid peroxidation are enhanced. Thus, the enhancement of both ferric ion reduction and lipid peroxidation may be due to oxalate increasing the solubility of the ferric ion. Increasing the oxalate concentration such that the oxalate/ferric ion ratio favored formation of the 2:1 and 3:1 complexes resulted in inhibition of iron reduction and lipid peroxidation. Our results confirm that hydroxyl radical formation occurs via the 2,5-DMBQ redox cycle.A prerequisite to gaining access to the cellulose and hemicellulose components of woody biomass is the circumvention of the lignin barrier. Filamentous fungi, the predominant degraders of wood, have evolved at least two mechanisms to circumvent this barrier. White rot fungi circumvent the lignin barrier by degrading it with extracellular peroxidases (14, 47), with eventual degradation to the level of CO 2 (28). In contrast, brown rot fungi cannot degrade the lignin component to CO 2 . However, these fungi can access the cellulose components with minimal modification of the lignin. These modifications include demethylation of aryl methoxy groups and ring hydroxylation (for a more extensive review, see reference 29).Due to the limited size of the wood pores and the nonspecific nature of wood degradation, Cowling and Brown (12) suggested that low-molecular-weight oxidants are the initial agents in wood decay. Koenigs (33) showed that a number of wood-decomposing fungi produce H 2 O 2 and noted the similarities between wood treated with the hydroxyl radical and with brown rot fungi (34). Illman et al. (23) subsequently detected the hydroxyl radical in incubations with the brown rot fungus Poria placenta by use of electron spin resonance and spin trapping agents. Further supporting the involvement of the hydroxyl radical is the formation of 3-hydroxy derivatives (the expected products from a hydroxyl radical attack) of phthalic hydrazide in incubations with brown rot fungi (5).The most likely nonphotochemical source of the hydroxyl radical is Fenton's reagent, defined by the following chemistry: The quinone undergoes cyclic oxidation-reduction reactions, serving as a shuttle for electrons from intracellular donors to extracellular acceptors. Although a similar mechanism has been proposed for white rot fungi (4, 17, 18) for h...

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“…Besides their role in extending the kind and number of lignin units that can be oxidized by the action of laccase, natural mediators are important because ligninolytic enzymes have to act indirectly during the early phases of plant cell wall degradation due to size exclusion limitations (13,14). Other small molecular agents participating in lignin degradation and produced directly or indirectly by ligninolytic enzymes include manganic ion (Mn 3ϩ ) (24,27,50), the cationic radical of the fungal metabolite veratryl (3,4-dimethoxybenzyl) alcohol (26), and activated oxygen species such as the hydroxyl radical (HO ⅐ ) and superoxide anion radical (O 2 ⅐Ϫ ) (2,15,27). Except for O 2 ⅐Ϫ , all of these compounds are able to oxidize lignin units.…”

mentioning

confidence: 99%

Oxygen Activation during Oxidation of Methoxyhydroquinones by Laccase from Pleurotus eryngii

Guillén

Muñoz

Gómez-Toribio

et al. 2000

Appl Environ Microbiol

105

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Oxygen activation during oxidation of the lignin-derived hydroquinones 2-methoxy-1,4-benzohydroquinone (MBQH 2 ) and 2,6-dimethoxy-1,4-benzohydroquinone (DBQH 2 ) by laccase from Pleurotus eryngii was examined. Laccase oxidized DBQH 2 more efficiently than it oxidized MBQH 2 ; both the affinity and maximal velocity of oxidation were higher for DBQH 2 than for MBQH 2 . Autoxidation of the semiquinones produced by laccase led to the activation of oxygen, producing superoxide anion radicals (

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Hydroxyl Radical Activity Associated with the Growth of White-Rot Fungi

Cited by 75 publications

References 26 publications

Cloning and characterization of the genes encoding the high-affinity iron-uptake protein complex Fet3/Ftr1 in the basidiomycete Phanerochaete chrysosporium

Cloning and characterization of the genes encoding the high-affinity iron-uptake protein complex Fet3/Ftr1 in the basidiomycete Phanerochaete chrysosporium

Effect of pH and Oxalate on Hydroquinone-Derived Hydroxyl Radical Formation during Brown Rot Wood Degradation

Oxygen Activation during Oxidation of Methoxyhydroquinones by Laccase from Pleurotus eryngii

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