Characterization of a heat-active archaeal β-glucosidase from a hydrothermal spring metagenome

Thermostable enzymes are required for application in a wide range of harsh industrial processes. High stability and activity at elevated temperatures, as well as high tolerances toward various reagents and solvents, are needed. In this work, a glycoside hydrolase family 1 beta-glucosidase (Bgl1) of archaeal origin was isolated from a hydrothermal spring metagenome. The enzyme showed a broad substrate spectrum with activity toward cellobiose, cellotriose and lactose. Compared to most enzymes, extremely high specific activity with 3195 U/mg was observed at 90 degrees C and pH 6.5. Bgl1 was completely stable at pH 4.5-9.5 for 48h at 4 degrees C. More than 40% of activity was measured at 105 degrees G. A thermal activation was observed at 90 degrees C after 30 min. Enzyme stability was enhanced (5- and 7-fold) after applying pressure of 100 and 200 bar at 90 degrees C for 2h, respectively. The affinity of the beta-glucosidase to its substrate was significantly increased in the presence of AICl3. The Ki value for glucose was 150 mM. These distinctive characteristics distinguish Bgl1 from other enzymes described so far and make this enzyme suitable for application in numerous processes that run at high temperatures. (c) 2014 Elsevier Inc. All rights reserved.