[Expression and characterization of a bifunctional thermal β-glucosidase IuBgl3 from thermophilic archaeon ].

β-glucosidase has important applications in food, medicine, biomass conversion and other fields. Therefore, exploring β-glucosidase with strong stability and excellent properties is a research hotspot. In this study, a GH3 family β-glucosidase gene named was successfully cloned from . Sequence analysis showed that the full length of was 2 106 bp, encoding 702 amino acids, with a theoretical molecular weight of 77.0 kDa. The gene was cloned and expressed in . and the enzymatic properties of purified IuBgl3 were studied. The results showed that the optimal pH and temperature for NPG hydrolysis were 5.0 and 85 ℃, respectively. The enzyme has good thermal stability, and more than 85% of enzyme activity can be retained after being treated at 80 ℃ for2 h. This enzyme has good pH stability and more than 85% of its activity can be retained after being treated at pH 4.0-11.0 for 1 h. It was found that the enzyme had high hydrolysis ability to -nitrophenyl β-d-glucoside (NPG) and -nitrophenyl β-d-xylopyranoside (NPX). When NPG was used as the substrate, the kinetic parameters and were 0.38 mmol and 248.55 μmol/(mg·min), respectively, and the catalytic efficiency / was 6 149.20 smmol. Most metal ions had no significant effect on the enzyme activity of IuBgl3. SDS completely inactivated the enzyme, while EDTA increased the enzyme activity by 30%. This study expanded the β-glucosidase gene diversity of the thermophilic archaea GH3 family and obtained a thermostable acid bifunctional enzyme with good industrial application potential.