Biochemical Characterization of an Extracellular Laccase From Pleurotus ostreatusARC280

摘要

An extracellular laccase from Pleurotus ostreatus ARC280 was characterized in terms of its catalytic stability and its effectiveness as a biocatalyst under various reaction conditions when using syringaldazine as a model substrate. Results obtained indicated that optimum degree of temperature for activity was found to be 50°C. Thermal stability studies indicated that Pl. ostreatus ARC280 crude cell-free filtrate retained laccase activity after heat exposure to 50, 60 and 70°C for 60 min. by about 85.63, 70.29 and 23.80 % respectively. Concerning pH stability, the crude enzyme retained 30.84, 64.86, 77.50, 90.31 and 86.72 % of its initial activity after 30 hrs of incubation at pH 3.0, 5.0, 7.0, 9.0 and 10.0, respectively. Optimum laccase activity was recorded at pH 6.0, 3.0, 4.5 and for syringaldazine (SGZ), 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and 2,6-dimethoxyphenol (DMP), respectively. EDTA (at different concentrations) was found to inhibit laccase activity. The enzyme was inhibited by the addition of Hg2+ or Cu2+ (1x10-1 and 5x10-2M) to the reaction mixture, however Mn2+ (2.5x10-3M) caused laccase activation by about 170 %.