Full Length Research Paper

Purification and characterization of β-glucosidase from Reticulitermes flaviceps and its inhibition by valienamine and validamine

Ya-Ping Xue, Li-Qun Jin, Zhi-Qiang Liu, Jian-Fen Zhang and Yu-Guo Zheng*

Institute of Bioengineering, Zhejiang University of Technology, Hangzhou 310014, China.

*Corresponding author. E-mail: zhengyg@zjut.edu.cn. Tel.: +86-571-88320630. Fax: +86-571-88320630.

Accepted 21 October, 2008

β-Glucosidase plays a very important role in the carbohydrate metabolism and it is the key enzyme that releases glucose for use as an energy and carbon source for termite. The β-glucosidase from the salivary glands of Reticulitermes flaviceps was purified in this study. The molecular mass of the purified enzyme was estimated to be 93.6 kDa based on its mobility in SDS-PAGE. The β-Glucosidase was stable at pH ranging from 5.0 - 6.8 and below 45°C. Its optimal temperature and pH were 35 - 40°C and 5.2 - 6.0, respectively. The β-Glucosidase was competitively inhibited by valienamine and validamine in vitro. The inhibition was pH-dependent and dose-dependent. The maximum inhibitory capacity of valienamine and validamine was at the optimal pH of this enzyme. The K_i values of valienamine and validamine were 1.3 and 1.9 mM, respectively, and the IC₅₀s of valienamine and validamine were observed at 1.92 and 2.92 mM, respectively.

Key words: Reticulitermes flaviceps; β-glucosidase; valienamine; validamine; inhibition.