Enzymes laccase

Although the use of mediator compounds is scarcely applicable in deca-BDE in situ bioremediation processes, it is important to consider whether their presence enhances the degradation of the pollutant by the enzyme laccase because it is known that the fungus is able to produce naturally certain compounds that can act as mediators in pollutant degradation by laccase and this study would show the extent of their effect on deca-BDE degradation in case that laccase was involved. 

The immobilization of the white rot fungus F. trogii in Na-ALG beads allowed the decolorization of the dye Acid Black 52 in a stirred tank reactor operated in batch [55]. Three enzymes, laccase, MnP, LiP, secreted by fungus were reported during decolorization process. Results showed that laccase enzyme activity increased with increasing alginate concentration from 0 to 4%. Cell growth at immobilized cultivation was maintained more stably than suspended cultivation. Total amount of removed dye was reported to be 469 mg/L for immobilized cultures and 440 mg/L for suspended cultures. 

Copper, like iron, is frequently encountered in reactions involving dioxygen. The copper enzyme laccase catalyses the oxidation of uroshiol (the same poisonous substance found in poison oak and ivy) in the production of Japanese lacquer. It is the products of uroshiol oxidation, which are responsible for the lacquer s remarkable material properties. 

Figure 5. ESR spectra of crude enzyme, laccases I, and III. (a) Crude enzyme, (b) laccase I, (c) laccase HI.

Operation of the latter mechanism has also been invoked for the oxidation of X-substituted benzyl alcohols with TEMPO and the enzyme laccase becanse the redox potential of the enzyme (0.78 is adeqnate for the oxidation of TEMPO to oxoammonium ion (0.8 Strangely enough, no linear correlation of the log A x/ h ratios... 

The aerobic oxidation of alcohols mediated by TEMPO, used in combination with other catalysts, such as CuBr Me2S,31 RuCl2(PPh3)332 or the enzyme laccase,33 must also be mentioned. 

Pal et al. (1994) compared the catalysis of oxidative coupling reactions of various phenolic compounds by the enzymes, laccase and tyrosinase, and mineral catalyst, birnessite. Birnessite acts as a heterogeneous catalyst whereas laccase and tyrosinase function as homogeneous catalysts. Laccase and tyrosinase continue to oxidize catechol after repeated additions of the chemical, while birnessite lost its oxidizing activity after the first addition of catechol (Figure 2.20). In the case of birnessite,... 

Calculated as percentage of the specific activity of the free enzyme (laccase = 27pmolmin 1 peroxidase = 97.7 pmol min-1). 

In some cases, substrates and enzymes are not soluble in the same solvent. To achieve efficient substrate conversion, a large interface between the immiscible fluids has to be established, by the formation of microemulsions or multiple-phase flow that can be conveniently obtained in microfluidic devices. Until now only a couple of examples are published in which a two-phase flow is used for biocatalysis. Goto and coworkers [431] were first to study an enzymatic reaction in a two-phase flow in a microfluidic device, in which the oxidation ofp-chlorophenol by the enzyme laccase (lignin peroxidase) was analyzed (Scheme 4.106). The surface-active enzyme was solubilized in a succinic acid aqueous buffer and the substrate (p-chlorophenol) was dissolved in isooctane. The transformation ofp-chlorophenol occurred mainly at... 

We illustrate these aspects of metalloprotein dynamics at surfaces by two specific proteins. One is the two-centre bacterial di-heme protein cyt c4 from Pseudomonas stutzeri, and the other is the fungal four-centre redox enzyme laccase from Polyporus versicolor. 

It has been shown [9] that the copper-dependent oxidase enzyme, laccase, in combination with TEMPO or derivatives thereof, is able to catalyze the aerobic oxidation of the primary alcohol moieties in starch (Fig. 10.2). There is currently considerable commercial interest in laccases for application in pulp bleaching (as a replacement for chlorine) in paper manufacture and remediation of phenol-containing waste streams [10]. 

Azinobis(3-ethylbenzothiazoline-6-sulfonic acid), namely ABTS-(NH4)2 (518), is found to be an adequate cosubstrate (or mediator) in the enzymatic oxidation of methyl groups on aromatic rings, lihe mediator (518) acts as a single-electron donor and activator of the enzyme (laccase) but does not function as oxidant of the substrate <9SJOC4320>. 

M Fabbrini, C Galh, P Gentih, D MacchiteUa. An oxidation of alcohols by oxygen with the enzyme laccase and mediation by TEMPO. Tetrahedron Lett. 42(43) 7551-7553, 2001. 

We have investigated in-situ STM of the small single-metal redox proteins cytochrome c (MW 12 kDa) and azurin ( 14 kDa), and the larger four copper-enzyme laccase (MW 64 kDa), all involved in natural ET [51, 54, 55]. The choice rested on the following considerations ... 

In the following discussion we will consider the properties of three different classes of this general type of enzyme laccases, ceruloplasmin, and ascorbic acid oxidase. Pertinent data are assembled in Table 2. Each of these enzymes catalyses the general reactions ... 

Methylene blue acted as a mediator of electrons providing electrical contact between the electrode and the solution-resident enzyme laccase (Fig. 10.5.7) catalyzing reduction of oxygen to water [46], The catalytic effect is revealed by the wave shape of the cyclic voltammetry curve in the oxygen-saturated solutions and its increased limiting current. 

Figure 7 Influence of composition (in weight percent) on rate of pyrocatechol oxidation. The enzyme laccase was added to a microemulsion based on AOT-octane-aqueous buffer. The value of kca in bulk water is 28 s . (From Ref. 44.)...

Anhydrovinblastine (126) was formed in 56% yield by an enzyme (laccase)-catalyzed coupling of catharanthine (124) and vindoHne (123) (Scheme 5). °... 

Coniferyl alcohol is dehydrogenated in vivo under the influence of the enzyme laccase. The dehydroconiferyl alcohol free radical produced can react further via three mesomorphic forms ... 

Polymerization of coniferyl alcohol begins with a dehydrogenation through the action of the enzyme laccase. This produces the radical of... 

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