Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

A glucose/O2 biofuel cell (BFC) possessing a pH-dependent power output was fabricated by taking porous carbon (PC) as the matrix to load glucose oxidase or fungi laccase as the catalysts. The electrolytes in the anode and cathode compartments contain ferrocene monocarboxylic acid and 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt as the mediators, respectively. The power of the BFC was enhanced significantly by using PC as the matrix, rather than glassy carbon electrode. Additionally, the power output of the BFC decreases as the pH of the solution increases from 4.0 to 7.0, which provides a simple and efficient method to achieve the required power output. More importantly, the BFC can operate at pH 6.0, and even at pH 7.0, which overcomes the requirement for cathode solutions of pH<5.0 when using fungi laccase as a catalyst. Operation of the BFC at neutral pH may provide a means to power medical devices implanted in physiological systems. The facile and low-cost fabrication of this BFC may enable its development for other applications.
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PMID:A low-cost biofuel cell with pH-dependent power output based on porous carbon as matrix. 1596 3

Nanostructured reversed micelles induce a high laccase activity in organic solvents, because enzymes can maintain their highly dimensional structure in water pools of reversed micelles [RMs]. Laccase attracts considerable attention as a novel industrial enzyme due to its high capability to catalyze the oxidation of aromatic compounds. The catalytic activities of lyophilized laccase and laccase entrapped in RMs were compared using an oxidative reaction. Laccase hosted in an anionic RM effectively catalyzed the oxidative reaction in various organic solvents, while lyophilized laccase exhibited no such catalytic activity. To optimize the preparation and reaction conditions for laccase in RMs, we examined the effects of pH of water pools of RMs, the concentrations of both enzyme and surfactant for the preparation of RMs, the hydration ratio (Wo), and the reaction temperature on laccase catalytic activity in organic media. Laccase entrapped in RMs exhibited the highest catalytic activity in isooctane under the following conditions: bis-2-ethylhexyl sulfosuccinate sodium salt (AOT) of 100 mM, pH 6.0, Wo=40, and reaction temperature of 60 degrees C. Under the optimum conditions, environmental pollutants such as bisphenol A, 2,4-dichlorophenol and 2,4,6-trichlorophenol were effectively degraded in 3 h.
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PMID:Catalytic activity of laccase hosted in reversed micelles. 1623 60

The effect of laccase and transglutaminase (TG) on cross-linking, gelation, and thermal stability of salt-soluble chicken-breast myofibril proteins was investigated at pH 6. Both enzymes modified the protein pattern detected by SDS-PAGE. Identification of proteins by peptide mass mapping showed that myosin heavy chain (MHC) and troponin T were the most affected proteins. These proteins faded or disappeared as a function of the incubation time with both enzymes on SDS-PAGE. The molecular weight of actin was not, however, affected by either enzyme. The effects that the enzymes had on the gel formation of chicken-breast myofibrils were studied in 0.35 and 0.60 M NaCl solutions at 3% protein content and a constant temperature of 40 degrees C by using a small deformation viscoelastic measurement. TG substantially increased the storage modulus (G') of 3% protein in 0.35 M NaCl. Without the enzymes, gelation was insignificant in 0.35 M NaCl. The increased solubility of the proteins at 0.60 M NaCl intensified gelation with TG. G' increased 32 and 64% at dosages of 10 and 100 nkat of TG, respectively. Also, laccase increased G' of the gel in 0.60 M salt concentration. However, a high laccase dosage decreased the magnitude of G' below the control level. Differential scanning calorimetric (DSC) measurements indicated slightly reduced myosin heat stability after TG pretreatment and increased actin heat stability with both enzymes. Maximum transition temperatures did not alter with either enzyme.
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PMID:Enzyme-aided modification of chicken-breast myofibril proteins: effect of laccase and transglutaminase on gelation and thermal stability. 1627 27

There has been increasing interest in extracellular enzymes from white rot fungi, such as lignin and manganese peroxidases, and laccases, due to their potential to degrade both highly toxic phenolic compounds and lignin. The optimum cultivation conditions for laccase production in semi-solid and liquid medium by Trametes versicolor, Trametes villosa, Lentinula edodes and Botrytis cinerea and the effects of laccase mediator system in E1 effluent were studied. The higher laccase activity (12756 U) was obtained in a liquid culture of T. versicolor in the presence of 1 mM of 2,5-xylidine and 0.4 mM copper salt as inducers. The effluent biotreatments were not efficient in decolorization with any fungal laccases studied. Maximum phenol reduction was approximately 23% in the absence of mediators from T. versicolor. The presence of 1-hydroxybenzotriazole did not increase phenol reduction. However, acetohydroxamic acid, which was not degraded by laccase, acted very efficiently on E1 effluent, reducing 70% and 73% of the total phenol and total organic carbon, respectively. Therefore, acetohydroxamic acid could be applied as a mediator for laccase bioremediation in E1 effluent.
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PMID:Laccase induction in fungi and laccase/N-OH mediator systems applied in paper mill effluent. 1637 74

The carbon nanotubes-chitosan (CNTs-CS) composite provides a suitable biosensing matrix due to its good conductivity, high stability, and good biocompatibility. Enzymes can be firmly incorporated into the matrix without the aid of other cross-linking reagents. The composite is easy to form insoluble film in solution above pH 6.3. Based on this, a facilely fabricated amperometric biosensor by entrapping laccase into the CNTs-CS composite film has been developed. At pH 6.0, the fungi laccase incorporated into the composite film remains better catalytic activity than that dissolved in solution. The system is in favor of the accessibility of substrate to the active site of laccase, thus the affinity to substrates is improved greatly, such as 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS), catechol, and O2 with Km values of 19.86 microM, 9.43 microM, and 3.22 mM, respectively. The major advantages of the as-prepared biosensor are: detecting different substrates (ABTS, catechol, and O2), possessing high affinity and sensitivity, durable long-term stability, and facile preparation procedure. On the other hand, the system can be applied in fabrication of biofuel cells as the cathodic catalysts based on its good electrocatalysis for oxygen reduction. It can be extended to immobilize other enzymes and biomolecules, which will greatly facilitate the development of biosensors, biofuel cells, and other bioelectrochemical devices.
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PMID:Facile preparation of amperometric laccase biosensor with multifunction based on the matrix of carbon nanotubes-chitosan composite. 1638 97

We previously showed that eight laccase genes (Lac 1-Lac 8) are preferentially expressed in differentiating xylem and are associated with lignification in loblolly pine (Pinus taeda) [Sato et al. (2001) J Plant Res 114:147-155]. In this study we generated transgenic tobacco suspension cell cultures that express the pine Lac 1 and Lac 2 proteins, and characterized the abilities of these proteins to oxidize monolignols. Lac 1 and Lac 2 enzymatic activities were detected only in the cell walls of transgenic tobacco cells, and could be extracted with high salt. The optimum pH for laccase activity with coniferyl alcohol as substrate was 5.0 for Lac 1 and between 5.0 and 6.0 for Lac 2. The activities of Lac 1 and Lac 2 increased as the concentration of CuSO(4) in the reaction mixtures increased in the range from 1 to 100 microM. Both enzymes were able to oxidize coniferyl alcohol and to produce dimers of coniferyl alcohol. These results are consistent with the hypothesis that Lac 1 and Lac 2 are involved in lignification in differentiating xylem of loblolly pine.
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PMID:Characterization of two laccases of loblolly pine (Pinus taeda) expressed in tobacco BY-2 cells. 1695 31

A convenient method for the measurement of the catalytic activity of laccase is proposed based on the voltammetric determination of catalytic reaction substrates: 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS) and 1,4-benzenediol (hydroquinone). The measurement performed using microelectrodes working under spherical diffusion conditions is both accurate and simple, and allows to monitor parallely the consumption of substrate and formation of product of the catalytic reaction. The method proposed in this paper was compared with the two generally employed procedures based on oxygen measurement by Clark electrode and on spectrophotometry. The procedure described in the present paper was found to be simpler and more reproducible results were obtained than using Clark electrode. Compared to spectrophotometry a larger range of catalytic reaction substrates can be studied including colorless compounds.
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PMID:Voltammetric determination of catalytic reaction parameters of laccase based on electrooxidation of hydroquinone and ABTS. 1711 61

Both native Trametes hirsuta laccase and the same laccase modified with palmytic chains to turn it more hydrophobic were prepared and studied with cyclic voltammetry and Raman spectroscopy. Native laccase immobilized in the monoolein cubic phase was characterized with resonance Raman spectroscopy, which demonstrated that the structure at the "blue" copper site of the protein remained intact. The diamond-type monoolein cubic phase prevents denaturation of enzymes on the electrode surface and provides contact of the enzyme with the electrode either directly or through the mediation by electroactive probes. Direct electron transfer for both laccases incorporated into a lyotropic liquid crystal was obtained under anaerobic conditions, whereas bioelectrocatalytic activity was shown only for the native enzyme. The differences in electrochemical behavior of native and hydrophobic laccase as well as possible mechanisms of direct and mediated electron transfers are discussed. The Michaelis constant for 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS2-), KMapp, and the maximal current, Imax, for the native enzyme immobilized onto the electrode were estimated to be 0.24 mM, and 5.3 microA, respectively. The maximal current density and the efficiency of the catalysis, Imax/KMapp, were found to be 73 microA cm-2 and 208.2 microA cm-2 mM-1, respectively, and indicated a high efficiency of oxygen electroreduction by the enzyme in the presence of ABTS2- in the cubic-phase environment. Rate constants were calculated to be 7.5x10(4) and 3.6x10(4) M-1 s-1 for native and hydrophobic laccase, respectively.
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PMID:Properties of native and hydrophobic laccases immobilized in the liquid-crystalline cubic phase on electrodes. 1715 64

A method of enzymatic synthesis of electroconductive polyaniline on the micelles of dodecylben-zenesulfonic acid sodium salt (DBSNa) is proposed. The high potential laccase from the basidiomycete Trametes hirsuta was used as a biocatalyst. The conditions for polyaniline synthesis were optimized (pH 4.0; reagent concentrations, 10-20 mM; and aniline/DBSNa ratio, 2: 1). The resulting product was electrochemically active in the range of potentials from -200 to 600 mV, electroconductive, and capable of reversible dedoping with a change in pH of solution.
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PMID:[Micellar laccase-catalyzed synthesis of electroconductive polyaniline]. 1866 52

The effect of bubble-free oxygenation on the stability of a bi-enzymatic system with redox mediator regeneration for the conversion of lactose to lactobionic acid was investigated in a miniaturized reactor with bubbleless oxygenation. Earlier investigations of this biocatalytic oxidation have shown that the dispersive addition of oxygen can cause significant enzyme inactivation. In the process studied, the enzyme cellobiose dehydrogenase (CDH) oxidizes lactose at the C-1 position of the reducing sugar moiety to lactobionolactone, which spontaneously hydrolyzes to lactobionic acid. 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt was used as electron acceptor for CDH and was continuously regenerated (reoxidized) by laccase, a blue multi-copper oxidase. Oxygen served as the terminal electron acceptor of the reaction and was fully reduced to water by laccase. The overall mass transfer coefficient of the miniaturized reactor was determined at 30 and 45 degrees C; conversions were conducted both in the reaction-limited and diffusion-limited regime to study catalyst inactivation. The bubbleless oxygenation was successful in avoiding gas/liquid interface inactivation. It was also shown that the oxidized redox mediator plays a key role in the inactivation mechanism of the biocatalysts unobserved during previous studies.
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PMID:Bubble-free oxygenation of a bi-enzymatic system: effect on biocatalyst stability. 1869 49


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