RESUMO
Given the upwelling of a variety of potential applications laccases could participate in, it would be fitting to equally make available laccases that are well suited for the aforementioned. Therefore historian understanding of the catalytic and physicochemical properties is desirable. Owing to this, the biochemical properties of the crude laccases from Achromobacter xylosoxidans HWN16 (Hb9c) and Citrobacter freundii LLJ 16 (Ie1c) were assessed. Furthermore, a hint of the molecular basis for their production from respective organisms was presented. Results showed that both laccases were tolerant, and sometimes had their activities improved by the set of parameters tested. They were active at broad range of temperature (0-90 °C), pH (3-11), and were equally thermo- and pH-stable. Their activities were either improved, or left unabated by cations, detergents, and chloride (5-40%), however, the highlight of the study was their augmented activity, when they were incubated with certain concentrations of fluoride (2-20%), a potent inhibitor. They were depicted to have multiple homologous laccase encoding genes, on molecular evaluation, which may be responsible the conferral of these remarkable qualities they possess. Therefore, the laccases might be beneficial, if employed in formulations for a wide range of environmental and biotechnological applications. Moreover, the molecular machinery of their production be exploited for economical benefits in the immediate future.
RESUMO
The conditions for the sulfhydryl oxidase (SOX) production and activity from an Egyptian isolate of Aspergillus niger were optimized. Purification and determination of the kinetic properties (K(m) and V(max)) of the purified enzyme have been done. The possibility for the SOX induction using L-Cys (as a natural substrate) was studied to determine whether SOX could be produced as an inducible enzyme in addition to being a constitutive one (i.e. whether induction leads to increase SOX production and activity or not). The optimum temperature and pH for its activity were found to be 60 degrees C and 5.5, respectively. The activity of the induced intracellular SOX, was measured according to Ellman's method using the standard GSH oxidation where it reached 94% while that of non-induced one reached only 27.6%. This wide difference in activity between the induced and non-induced SOX indicates the successful L-Cys-induction of the SOX production (i.e. SOX from A. niger AUMC 4947 is an inducible enzyme). Molecular characterization of the pure SOX revealed that it is constituted of two 50-55 KDa subunits. K(m) and V(max) were found to be 6.0 mM and 100 microM/min/mg respectively.
