Characterization of a thermostable beta-glucosidase (Bg1B) from Thermotogamaritima showing transglycosylation activity

A beta -glucosidase gene (bglB) of an extremely thermophilic eubacterium, T hermotoga maritima was expressed in Esherichia coli to yield the active enz yme. The cloned enzyme was purified to homogeneity by heat treatment and io n exchange chromatographies. The purified enzyme gave a single band on SDS- PAGE with a molecular weight of 81 kDa. The estimated K-m and k(cat) values for p-nitrophenyl beta -D-glucopyranoside were 0.0039 mM and 6.34 s(-1), r espectively. The purified enzyme was optimally active at pH 5.0 (85 degrees C), however, it also displayed higher activity at acidic pH (optimum pH 3.5 ) at a lower temperature (70 degreesC). An investigation into the effect of straight chain alcohols and organic compounds on the activity of enzyme re vealed that alcohols had a stimulatory effect, possibly due to the occurren ce of transglycosylation. Because of its thermostability and transglycosyla tion properties, this enzyme displays potential as a catalyst for biotechno logical applications. (C) 2001 Elsevier Science B.V. All rights reserved.