Laccases action mechanism

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],... 

Such unspecific oxidative attack is also discussed as a possible route in the biodegradation fate of PVA. Oxidation of PVA should be possible, as very aggressive oxidative species can be generated by the extracellular enzyme mixtures of wood-rotting fungi. Unspecific oxidative incidents are to be expected when strongly oxidising low molecular mediators react with PVA, a mechanism that is described as the indirect action of laccase enzymes [77]. Reports about the beneficial... 

The elaborate mechanism by which blue oxidases react with dioxygen to produce water was tackled by studying the possible role of H202. We have observed the formation of a stable and high affinity complex between tree laccase and H202. Moreover, the finding that the oxidation of the reduced enzyme with H202 follows a pattern which is different from that operative in the reduction of the oxidized enzyme may have important implications for the mechanism of action of laccase. 

In contrast to tree and fungal laccase, whose molecular parameters and mechanisms of action have been thoroughly investigated (8), few such studies have been reported for ascorbate oxidase. This is mainly because of the relatively diflScult isolation and purification procedure of ascorbate oxidase in comparison with laccase. Furthermore, this enzyme appears to be more sensitive to environmental factors such as ionic strength of the buffer medium, its pH, or the presence of extraneous metal ions. Consequently, many samples isolated over a long period were found to be homogeneous from the standpoint of the protein biochemist but appeared inhomogeneous with respect to the catalytically active copper sites (9). 

Most lignans are obtained optically active and, presumably, enantiomerically pure. However, the phenolic coupling processes catalysed by H2C>2-dependent peroxidases, Ch-requiring laccases or phenol oxidases yield racemic products. A protein without an active centre has been isolated that in presence of an oxidase produces stereoselective bimolecular phenoxy radical coupling reactions in in vitro lignan biosynthesis. Its mechanism of action is presumed to involve capture of -coniferyl alcohol-derived free radical intermediates [34],... 

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