Enhanced activity and stability of cellobiase (β-glucosidase: EC 3.2.1.21) produced in the presence of 2-deoxy- d-glucose from the fungus Termitomyces clypeatus

Abstract

Generally less glycosylation or deglycosylation has a detrimental effect on enzyme activity and stability. Increased production and secretion of cellobiase was earlier obtained in the presence of the glycosylation inhibitor 2-deoxy- d-glucose in filamentous fungus Termitomyces clypeatus [Mukherjee, S.; Chowdhury, S.; Ghorai, S.; Pal, S.; Khowala, S. Biotechnol. Lett. 2006, 28, 1773–1778]. In this study the enzyme was purified from the culture medium by ultrafiltration and gel-permeation, ion-exchange and high-performance liquid chromatography, and its catalytic activity was six times higher compared to the control enzyme. K m and V max of the purified enzyme were measured as 0.187 mM and 0.018 U mg −1, respectively, using pNPG as the substrate. The enzyme had temperature and pH optima at 45 °C and pH 5.4, respectively, and retained full activity in a pH range of 5–8 and temperatures of 30–60 °C. Interestingly less glycosylated cellobiase was resistant towards proteolytic as well as endoglycosidase-H digestion and showed higher stability than native enzyme due to increased aggregation of the protein. The enzyme also showed higher specific activity in the presence of cellobiose and pNPG and less susceptibility towards salts and different chemical agents. The β-glucosidase can be considered as a potentially useful enzyme in various food-processing, pharmaceutical and fermentation industries.