Comparative spectroscopic study of Syringaldazine oxidation catalyzed by laccase in reverse micelles of AOT and aqueous medium. Influence of the UVB light on the enzymatic kinetic parameters in both media.

Abstract

Laccase is a versatile enzyme for the oxidation of environmental contaminants and display great potential in many applications; however, it undergoes photo-degradation when irradiated with UVB light. The instability of this biomolecule can be improved by immobilization in different encapsulation media. In the present contribution, reverse micelles of AOT were used with this purpose. Moreover, the use of these kind of media can be relevant in the sense that they be able to mimetic the complexity of contaminated aquatic microenvironments where the enzymes can be used as biological remediation agents.The laccase activity from spectroscopic data, using syringaldazine as substrate has been studied in the absence and in the presence of reverse micelles of 0.15 M AOT/isooctane at W0 ([H2O]/[AOT]) =30, before and after irradiation of the enzyme with UVB light.The kinetic parameters, i.e. Michaelis-Menten constant (KM), catalytic constant (kCAT) and catalytic efficiency (kCAT / KM) were determinate in the micellar system and in aqueous medium and comparatively analyzed. From this comparison, it was found that the enzyme presents a considerably photo-protection when irradiated with UVB light in reverse micelles as compared with the aqueous medium. Moreover, taking into account the distribution of the substrate in the two pseudo-phases (micellar and organic solvent), the activity of the enzyme is significantly preserved in the micellar medium.