Hydroxyl Radical Activity in Brown-Rot Fungi Studied by a New Chemiluminescence Method

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

doi:10.1515/hfsg.1992.46.1.61

Cited by 78 publications

(47 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Moreover, growth of C. puteana and other brown rots in the presence of phthalic hydrazide led to formation of a 3-hydroxy derivative, as expected for attack by HO' on the aromatic ring (Backa et al, 1992).…”

Section: Introductionmentioning

confidence: 72%

A Mechanism for Production of Hydroxyl Radicals by the Brown-Rot Fungus Coniophora Puteana: Fe(III) Reduction by Cellobiose Dehydrogenase and Fe(II) Oxidation at a Distance from the Hyphae

Hyde

Wood²

1997

Microbiology

186

125

View full text Add to dashboard Cite

In timber infested by brown-rot fungi, a rapid loss of strength is attributed to production of hydroxyl radicals (HO.). The hydroxyl radicals are produced by the Fenton reaction [Fe(II)/H2O2], but the pathways leading to Fe(II) and H2O2 have remained unclear. Cellobiose dehydrogenase, purified from cultures of Coniophora puteana, has been shown to couple oxidation of cellodextrins to conversion of Fe(III) to Fe(II). Two characteristics of brown rot are release of oxalic acid and lowering of the local pH, often to about pH 2. Modelling of Fe(II) speciation in the presence of oxalate has revealed that Fe(II)-oxalate complexes are important at pH 4-5, but at pH 2 almost all Fe(II) is in an uncomplexed state which reacts very slowly with dioxygen. Diffusion of Fe(II) away from the hyphae will promote conversion to Fe(II)-oxalate and autoxidation with H2O2 as product. Thus the critical Fe(II)/H2O2 combination will be generated at a distance, enabling hydroxyl radicals to be formed without damage to the hyphae.

show abstract

Section: Introductionmentioning

confidence: 72%

A Mechanism for Production of Hydroxyl Radicals by the Brown-Rot Fungus Coniophora Puteana: Fe(III) Reduction by Cellobiose Dehydrogenase and Fe(II) Oxidation at a Distance from the Hyphae

Hyde

Wood²

1997

Microbiology

186

125

View full text Add to dashboard Cite

show abstract

“…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).…”

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

View full text Add to dashboard Cite

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...

show abstract

“…Although much remains unknown about their biodegradative mechanisms, there is growing evidence (2,8,11,13,21) that these fungi produce extracellular hydroxyl radicals (…”

mentioning

confidence: 99%

An NADH:Quinone Oxidoreductase Active during Biodegradation by the Brown-Rot Basidiomycete Gloeophyllum trabeum

Jensen

Ryan

Wymelenberg

et al. 2002

Appl Environ Microbiol

View full text Add to dashboard Cite

The brown-rot basidiomycete Gloeophyllum trabeum uses a quinone redox cycle to generate extracellular Fenton reagent, a key component of the biodegradative system expressed by this highly destructive wood decay fungus. The hitherto uncharacterized quinone reductase that drives this cycle is a potential target for inhibitors of wood decay. We have identified the major quinone reductase expressed by G. trabeum under conditions that elicit high levels of quinone redox cycling. The enzyme comprises two identical 22-kDa subunits, each with one molecule of flavin mononucleotide. It is specific for NADH as the reductant and uses the quinones produced by G. trabeum (2,5-dimethoxy-1,4-benzoquinone and 4,5-dimethoxy-1,2-benzoquinone) as electron acceptors. The affinity of the reductase for these quinones is so high that precise kinetic parameters were not obtainable, but it is clear that k cat /K m for the quinones is greater than 10 8 M ؊1 s ؊1 . The reductase is encoded by a gene with substantial similarity to NAD(P)H:quinone reductase genes from other fungi. The G. trabeum quinone reductase may function in quinone detoxification, a role often proposed for these enzymes, but we hypothesize that the fungus has recruited it to drive extracellular oxyradical production.

show abstract

Hydroxyl Radical Activity in Brown-Rot Fungi Studied by a New Chemiluminescence Method

Cited by 78 publications

References 13 publications

A Mechanism for Production of Hydroxyl Radicals by the Brown-Rot Fungus Coniophora Puteana: Fe(III) Reduction by Cellobiose Dehydrogenase and Fe(II) Oxidation at a Distance from the Hyphae

A Mechanism for Production of Hydroxyl Radicals by the Brown-Rot Fungus Coniophora Puteana: Fe(III) Reduction by Cellobiose Dehydrogenase and Fe(II) Oxidation at a Distance from the Hyphae

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

An NADH:Quinone Oxidoreductase Active during Biodegradation by the Brown-Rot Basidiomycete Gloeophyllum trabeum

Contact Info

Product

Resources

About