Inhibition mechanism of <i>Polyporus</i> laccase by fluoride ion

Naqui, Ali; Варфоломеев, С. Д.

doi:10.1016/0014-5793(80)80581-3

Cited by 38 publications

(32 citation statements)

References 8 publications

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“…Fluoride acts as a non-competitive inhibitor by binding to the T2/T3 copper cluster, blocking the ET pathway from the T1 site to the T2/T3 cluster [15][16][37][38]. This is confirmed by the complete removal of the biocatalytic activity of ThLc-modified nanoporous gold electrodes at a low concentration (2 mM) of F -( Fig.…”

Section: Resultsmentioning

confidence: 61%

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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Section: Resultsmentioning

confidence: 61%

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 binding of F ¹ to the T2/3 Cu site is widely reported. 5,20,32,33 In the current results, the ³30 mV shift in E 1/2 at a F ¹ concentration of 1 © 10 ¹3 mol dm ¹3 indicated that F ¹ bound to the T1 Cu site. For Cl ¹ inhibition, the ³30 mV in E 1/2 was insufficient to inhibit intramolecular electron transfer.…”

Section: ¹3mentioning

confidence: 52%

“…The inhibition mechanism of Lac was investigated by using spectrophotometrically method and a combination of spectroscopic and DFT studies. [17][18][19][20] Voltammetric studies on the halide inhibition was carried out, which suggested the ability to differentiate the inhibition modes of Lac by halides. 5,13 However, the mechanism of inhibition has not yet been clarified.…”

Section: Resultsmentioning

confidence: 99%

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Bioelectrocatalytic Oxygen Reaction and Chloride Inhibition Resistance of Laccase Immobilized on Single-walled Carbon Nanotube and Carbon Paper Electrodes

2016

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The rate of heterogeneous direct electron transfer of laccase immobilized on single-walled carbon nanotube (SWCNT) and carbon paper electrodes was evaluated by cyclic voltammetry and background-current-corrected steady-state linear voltammetry. These rates indicated that the molecular orientation of laccase immobilized on the SWCNT electrode was more favorable for direct electron transfer, than that of laccase immobilized on the carbon paper electrode. The inhibition of the bioelectrocatalytic O 2 reduction current of the two electrodes by chloride and fluoride were tested. The results indicated differing inhibition mechanisms by these two halides. Laccase immobilized on the SWCNT electrode exhibited high stability and high resistance to chloride inhibition.

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“…The effects of several known laccase inhibitors on the activity of LAP2 were examined using ABTS as substrate Naqui & Varfolomeev (1980). ‡ From Palmieri et al (1997).…”

Section: Kinetic Properties Of Lap2mentioning

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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Inhibition mechanism of Polyporus laccase by fluoride ion

Cited by 38 publications

References 8 publications

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

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

Bioelectrocatalytic Oxygen Reaction and Chloride Inhibition Resistance of Laccase Immobilized on Single-walled Carbon Nanotube and Carbon Paper 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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