Characterization of a thermostable β-glucosidase (BglB) from Thermotoga maritima showing transglycosylation activity

A β-glucosidase gene (bglB) of an extremely thermophilic eubacterium, Thermotoga maritima was expressed in Esherichia coli to yield the active enzyme. The cloned enzyme was purified to homogeneity by heat treatment and ion exchange chromatographies. The purified enzyme gave a single band on SDS-PAGE with a molecular weight of 81 kDa. The estimated Km and kcat values for p-nitrophenyl β-d-glucopyranoside were 0.0039 mM and 6.34 s−1, respectively. The purified enzyme was optimally active at pH 5.0 (85°C), however, it also displayed higher activity at acidic pH (optimum pH 3.5) at a lower temperature (70°C). An investigation into the effect of straight chain alcohols and organic compounds on the activity of enzyme revealed that alcohols had a stimulatory effect, possibly due to the occurrence of transglycosylation. Because of its thermostability and transglycosylation properties, this enzyme displays potential as a catalyst for biotechnological applications.