The structure and function of fungal laccases

Thurston, Christopher F.

doi:10.1099/13500872-140-1-19

Cited by 1,736 publications

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“…The molecular mass of this polypeptide of 55 kDa falls within the M r range reported for many fungal laccases, which can range from 50 to 90 kDa [2,3]. An approximate purification of 183 fold was achieved with a final yield of 12%.…”

Section: Purification and Molecular Propertiesmentioning

confidence: 80%

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An acid-stable laccase from Sclerotium rolfsii with potential for wool dye decolourization

Ryan

Schnitzhofer

Tzanov

et al. 2003

Enzyme and Microbial Technology

108

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The plant pathogen basidiomycete S. rolfsii secretes two laccases (SRL1 and SRL2) with molecular weights of 55 and 86 kDa, respectively. Laccase production was shown to be inducible by the addition of 2,5-xylidine to the cultural media. After treatment with a combination of chitinase and ␤-1,3-glucanase, two different laccases were isolated from the sclerotia depending on the stage of sclerotia development.The more prominent laccase, SRL1, was purified and found to decolourize the industrially important wool azo dye Diamond Black PV 200 without the addition of redox mediators. The enzyme (pI 5.2) was active in the acidic pH range, showing an optimal activity at pH 2.4, with ABTS as substrate. The optimum temperature for activity was determined to be 62 • C. Enzyme stability studies revealed that SRL1 was notably stable at 18 • C and pH 4.5, retaining almost full activity after a week. Oxidation of tyrosine was not detectable under the reaction conditions but the enzyme did oxidize a variety of the usual laccase substrates. SRL1 was strongly inhibited by sodium azide and fluoride. Dye solutions decolourized with the immobilized laccase were successfully used for redyeing.

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Section: Purification and Molecular Propertiesmentioning

confidence: 80%

“…Although primarily originating from fungi [2,3], laccases are widely distributed in nature and have also been detected in plants [4], insects [5] and bacteria [6]. These oxidative enzymes are particularly abundant in white-rot basidiomycete fungi, which are capable of degrading lignin in vivo.…”

Section: Introductionmentioning

confidence: 99%

An acid-stable laccase from Sclerotium rolfsii with potential for wool dye decolourization

Ryan

Schnitzhofer

Tzanov

et al. 2003

Enzyme and Microbial Technology

108

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“…Lc, together with ceruloplasmin, ascorbate oxidase, and bilirubin oxidase (BOx) belongs to the group of Cuproteins which are also known as blue multicopper oxidases. More than 60 types of Lc have been isolated from various type of plants, fungi and bacteria sources with different thermodynamic and kinetic properties [9][10]. Lc contains four copper ions classified according to their spectral characteristics into three types, T1, T2 and T3.…”

Section: Introductionmentioning

confidence: 99%

Direct electron transfer of Trametes hirsuta laccase adsorbed at unmodified nanoporous gold electrodes

Salaj-Kośla

Pöller

Schuhmann

et al. 2013

Bioelectrochemistry

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The enzyme Trametes hirsuta laccase undergoes direct electron transfer at unmodified nanoporous gold electrodes, displaying a current density of 28 A/cm 2 . The response indicates that ThLc was immobilised at the surface of the nanopores in a manner which promoted direct electron transfer, in contrast to the absence of a response at unmodified polycrystalline gold electrodes. The bioelectrocatalytic activity of ThLc modified nanoporous gold electrodes was strongly dependent on the presence of halide ions. Fluoride completely inhibited the enzymatic response, whereas in the presence of 150 mM Cl -, the current was reduced to 50% of the response in the absence of Cl -. The current increased by 40% when the temperature was increased from 20°C to 37°C. The response is limited by enzymatic and/or enzyme electrode kinetics and is 30% of that observed for ThLc co-immobilised with an osmium redox polymer. Keywords: Laccase, direct electron transfer, nanoporous gold 2 IntroductionElectron transfer (ET) reactions are ubiquitous in nature. Controlling the rate of these reactions can be of significant benefit in developing biochemical systems that utilise redox proteins and enzymes and in particular, in applications that provide power for implanted or portable electronic devices. ET can be achieved directly (direct electron transfer, DET) or by the use of mediators (mediated electron transfer, MET) to shuttle electrons between the redox centre of the enzyme and the electrode. However, mediators are unselective and can also give rise to interfering effects [1][2][3]. DET-based devices offer high selectivity and sensitivity due to the absence of mediators. In addition, devices based on DET operate at potentials close to the redox potential of the enzyme, maximising the potential difference between the cathode and anode for biofuel cell applications [2]. Moreover, DET can be used to provide detailed information on the kinetics and thermodynamics of the ET process. However, the low stability of the enzyme layer together with the long distances over which ET occurs, represent major obstacles for DET based devices. In addition, the shielding mechanism of the enzymatic redox centre by the protein shell can disrupt DET [2,4]. One approach in optimizing and enabling rapid DET is to design the electrode surface with an architecture which promotes efficient rates of ET. In this way the electrode morphology ensures the most efficient orientation of the enzymatic redox centre and facilitates communication with the electroactive surface. Porous electrodes can be used to encapsulate the enzyme within a network of cavities, shortening the distance for electron transfer to the redox active site, which will promote more efficient and rapid rates of electron transfer [5]. However, the number of redox enzymes capable of interacting directly with the electrode while catalyzing the enzymatic reaction is limited, with estimates of approximately 5% of all enzymes exhibiting such a response [6].DET in enzymes was first described in 1978 fo...

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“…ferrocyanide or iodide, with the concomitant fourelectron reduction of oxygen to water (Eggert et al, 1996 ;Reinhammar, 1984 ;Solomon et al, 1996 ;Thurston, 1994). Laccases are found in plants, insects and bacteria, but the most important sources of this enzyme are fungi.…”

Section: Abbreviationsmentioning

confidence: 99%

Characterization of the major laccase isoenzyme from Trametes pubescens and regulation of its synthesis by metal ions a aThe GenBank accession numbers for the lap2 and lap1a genes reported in this paper are AF414807 and AF414808, respectively.

et al. 2002

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The major laccase isoenzyme LAP2 secreted by the white-rot basidiomycete Trametes pubescens in response to high copper concentrations was purified to apparent electrophoretic homogeneity using anion-exchange chromatography and gel filtration. The monomeric protein has a molecular mass of 65 kDa, of which 18 % is glycosylation, and a pI value of 2 6. The pH optima of the laccase depend on the substrates oxidized and show bell-shaped pH activity profiles with an optimum of 3-4 5 for phenolic substrates such as 2,6-dimethoxyphenol or syringaldazine, while the non-phenolic substrates ABTS [2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)] and ferrocyanide show a monotonic pH profile with a rate increasing with decreasing pH. The catalytic efficiencies k cat /K m determined for some of its substrates were 48W10 6 , 47W10 6 , 20W10 6 and 7W10 6 M N1 s N1 for ABTS, syringaldazine, ferrocyanide and oxygen, respectively. Furthermore, the gene lap2 encoding the purified laccase was cloned and its nucleotide sequence determined. The gene consists of 1997 bp, with the coding sequence interrupted by eight introns and flanked by an upstream region in which putative CAAT, TATA, MRE and CreA consensus sequences were identified. Based on Northern analysis containing total RNA from both induced and uninduced cultures, expression of lap2 is highly induced by copper, which is also corroborated by an increase in laccase activity in response to copper. A stimulating effect of various other heavy metal ions on laccase synthesis was also observed. In addition to induction, a second regulatory mechanism seems to be repression of lap2 transcription by glucose.

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The structure and function of fungal laccases

Cited by 1,736 publications

References 32 publications

An acid-stable laccase from Sclerotium rolfsii with potential for wool dye decolourization

An acid-stable laccase from Sclerotium rolfsii with potential for wool dye decolourization

Direct electron transfer of Trametes hirsuta laccase adsorbed at unmodified nanoporous gold electrodes

Characterization of the major laccase isoenzyme from Trametes pubescens and regulation of its synthesis by metal ions a aThe GenBank accession numbers for the lap2 and lap1a genes reported in this paper are AF414807 and AF414808, respectively.

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