Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.10.3.2 (laccase)
 4,656 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

O(2) was electroreduced to water at 0.6 V (SHE) near neutral pH on the "wired" Pleurotus ostreatus laccase cathode. We previously reported high-current density (5 mA cm(-2)), four-electron electroreduction of O(2) to water on a "wired" Coriolus hirsutus laccase electrode at +0.7 V (SHE) in pH 5 in citrate buffer. Since the enzyme was inhibited by chloride and because its activity declined steeply when the pH was raised to neutral, the rate of O(2) electroreduction in a physiological buffer solution was only approximately 1% of that at pH 5 in absence of chloride. Here we show that substitution of the C. hirsutus laccase by laccase from P. ostreatus allows the upward extension of the pH range of O(2) electroreduction. The current density of the electrode made with laccase from P. ostreatus in pH 7 citrate buffer was approximately 100 microA cm(-2) and at pH 7 and in phosphate buffered NaCl (PBS, 20 mM phosphate, 0.1 M NaCl) it still retained 6% of its maximal (1 mA cm(-2)) current density at pH 5 in citrate buffer. The electrocatalyst consisted of the crosslinked P. ostreatus laccase and the electron conducting redox polymer PVI-Os(dmebpy)(tpy)(2+/3+) [PVI=poly(N-vinyl imidazole) with about 1/5th of the rings complexed with (Os-dmebpy-tpy)(2+/3+); dmebpy=4,4'-dimethyl-2,2'-bipyridine; tpy=2,2',6',2"-terpyridine].
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PMID:Electroreduction of O(2) to water at 0.6 V (SHE) at pH 7 on the "wired" Pleurotus ostreatus laccase cathode. 1239 57

The bacterially-expressed laccase, small laccase (SLAC) of Streptomyces coelicolor, was incorporated into electrodes of both direct electron transfer (DET) and mediated electron transfer (MET) designs for application in biofuel cells. Using the DET design, enzyme redox kinetics were directly observable using cyclic voltammetry, and a redox potential of 0.43 V (SHE) was observed. When mediated by an osmium redox polymer, the oxygen-reducing cathode retained maximum activity at pH 7, producing 1.5 mA/cm2 in a planar configuration at 900 rpm and 40 degrees C, thus outperforming enzyme electrodes produced using laccase from fungal Trametes versicolor (0.2 mA/cm2) under similar conditions. This improvement is directly attributable to differences in the kinetics of SLAC and fungal laccases. Maximum stability of the mediated SLAC electrode was observed at pH above the enzyme's relatively high isoelectric point, where the anionic enzyme molecules could form an electrostatic adduct with the cationic mediator. Porous composite SLAC electrodes with increased surface area produced a current density of 6.25 mA/cm2 at 0.3 V (SHE) under the above conditions.
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PMID:Oxygen-reducing enzyme cathodes produced from SLAC, a small laccase from Streptomyces coelicolor. 1809 78

Oxygen-reducing enzyme electrodes are prepared from laccase of Trametes versicolor and a series of osmium-based redox polymer mediators covering a range of redox potentials from 0.11 to 0.85 V. Experimentally obtained current density generated by the film electrodes is analyzed using a one-dimensional numerical model to obtain kinetic parameters. The bimolecular rate constant for mediation is found to vary with mediator redox potential from 250 s(-1) M(-1) when mediator and enzyme are close in redox potential to 9.4 x 10(4) s(-1) M(-1) when the redox potential difference is large. The value of the bimolecular rate constant for the simultaneously occurring laccase-oxygen reaction is found to be 2.4 x 10(5) s(-1) M(-1). The relationship between mediator-enzyme overpotential and bimolecular rate constant is used to determine the optimum mediator redox potential for maximum power output of a hypothetical biofuel cell with a planar cathode and a reversible hydrogen anode. For laccase of T. versicolor (E(e)(0) = 0.82), the optimum mediator potential is 0.66 V (SHE), and a molecular structure is presented to achieve this result.
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PMID:Kinetics of redox polymer-mediated enzyme electrodes. 1854 May 77