Laccase nature

Malmstrom, B.G., Mosbach, R., and Vanngard, T. 1959. An electron spin resonance study of the state of copper in fungal laccase. Nature 183 321-322. 

Quintanar L, Yoon J, Aznar CP, Palmer AE, Andersson KK, Britt RD, Solomon El. 2005. Spectroscopic and electronic structure studies of the trinuclear Cu cluster active site of the multicopper oxidase laccase nature of its coordination unsaturation. J Am Chem Soc 127 13832-13845. 

Hakulinen N, Kiiskinen LL, Kruus K, Saloheimo M, Paananen A, Koivula A, Rouvinen J. 2002. Crystal structure of a laccase from Melanocarpus albomyces with an intact trinuclear copper site. Nature Struct Biol 9 601-605. 

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. 

While direct electron transfer to laccases may help elucidate the mechanism of action of these enzymes it is unlikely that this process will supply sufficient power for a viable implantable biocatalytic fuel cell, because of difficulties associated with the correct orientation of the laccase and the two-dimensional nature of the biocatalytic layer on the surface. However, a recent attempt to immobilize laccase in a carbon dispersion, to provide electrodes with correctly oriented laccase for direct electron transfer, and a higher density of electrode material shows promise [53],... 

A similar problem occurs with beer stabilization. A serious problem in the brewing industry is the tendency of some beers to develop hazes during long-term storage due to protein precipitation that is usually stimulated by small quantities of naturally occurring proanthocyanidin polyphenols. In the same way as observed for wine, the excess polyphenols are traditionally removed by treatment with insoluble PVPP, with the same resulting problems. To resolve the problems, several authors have proposed the use of laccase, which forms polyphenol complexes that may be removed by filtration or other separation means. 

SSF containing wheat bran and soybean as a substrate was chosen for the production of ligninolytic enzymes for Funalia trogii ATCC200800 [18] as it mimics the natural environment of the WRF and permits the concentration of dyes by absorption process prior to biological treatment [4, 38, 39]. It is possible to stimulate the yield of laccase activity of Trametes versicolor by using several agricultural wastes [40]. 

Dye decolorizing potential of the WRF Ganoderma lucidum KMK2 was demonstrated for recalcitrant textile dyes. G. lucidum produced laccase as the dominant lignolytic enzyme during SSF of wheat bran, a natural lignocellulosic substrate. Crude enzyme shows excellent decolorization activity to anthraquinone dye Rema-zol Brilliant Blue R without redox mediator, whereas diazo dye Remazol Black-5 (RB-5) requires a redox mediator [43]. 

Various spectroscopic methods have been used to probe the nature of the copper centers in the members of the blue copper oxidase family of proteins (e.g. see ref. 13). Prior to the X-ray determination of the structure of ascorbate oxidase in 1989, similarities in the EPR and UV-vis absorption spectra for the blue multi-copper oxidases including laccase and ceruloplasmin had been observed [14] and a number of general conclusions made for the copper centers in ceruloplasmin as shown in Table 1 [13,15]. It was known that six copper atoms were nondialyzable and not available to chelation directly by dithiocarbamate and these coppers were assumed to be tightly bound and/or buried in the protein. Two of the coppers have absorbance maxima around 610 nm and these were interpreted as blue type I coppers with cysteine and histidine ligands, and responsible for the pronounced color of the protein. However, they are not equivalent and one of them, thought to be involved in enzymatic activity, is reduced and reoxidized at a faster rate than the second (e.g. see ref. 16). There was general concurrence that there are two type HI... 

Copper oxidases are widely distributed in nature, and enzymes from plants, microbes, and mammals have been characterized (104,105). The blue copper oxidases, which include laccases, ascorbate oxidases, and ceruloplasmin, are of particular interest in alkaloid transformations. The principle differences in specificity of these copper oxidases are due to the protein structures as well as to the distribution and environment of copper(II) ions within the enzymes (106). While an in vivo role in metabolism of alkaloids has not been established for these enzymes, copper oxidases have been used in vitro for various alkaloid transformations. 

Scheme 7.8 Selective laccase/mediator oxidation of the natural glycoside thiocolchicoside...

Laccases are oxidoreductases, primarily secreted by fungi, available in industrial quantities for use in the fabrics industry. Their natural role is in the breakdown of... 

Laccase is perhaps the metallo-enzyme most widely used for this aim. Laccases are a family of multicopper ( blue copper ) oxidases widely distributed in nature Many laccases have fungal origin, while others are produced in plants. They contain four Cu(II) ions, and catalyse the one-electron oxidation of four molecules of a reducing substrate with the concomitant four-electron reduction of oxygen to water . In view of their low redox potential, which is in the range of 0.5-0.8 V vs. NHE depending on the fungal source laccases typically oxidize phenols (phenoloxidase activity) or anilines. 

Fueled by the biological relevance, the initial steps of Cu-based O2 activation have attracted much interest in the last decades. Various, very different Cux/02 species that result from the reaction of dioxygen with Cu complexes have meanwhile been identified (Fig. 2) [70-90], where mononuclear species A and B as well as dinuclear type E and F species (and some tricopper systems as in, for example, laccase) are considered the most relevant in nature. 

---