Prokaryotic expression and characterization of the GH1 β-glucosidase Bgl59 from Devosia psychrophila

Abstract:

β-glucosidases have been widely used in food, medicine, bioenergy and other fields, and thus it is necessary to explore new and efficient β-glucosidases. [Objective] To realize the prokaryotic expression of a GH1 glucosidase derived from Devosia psychrophila and characterize the enzymatic properties of the expressed protein. [Methods] The gene encoding the β-glucosidase derived from D. psychrophila was synthesized, named bgl59, and then transformed into Escherichia coli BL21(DE3). After the gene expression was induced, and the obtained protein was purified and characterized for the enzymatic properties. [Results] Bgl59 had a molecular weight of 48.8 kDa, with the highest activity at 55 ℃ and pH 6.0. After treatment for 1 h within the range of pH 5.0–8.5, Bgl59 maintained the relative activity over 80%. Bgl59 had the highest hydrolysis ability for 4-nitrophenyl-β-d-glucopyranoside (pNPG) among the eight substrates tested, with the K_m of 3.090 mmol/L, V_max of 194 μmol/(min·mg), and k_cat of 159 s⁻¹. The presence of 1 mmol/L of Ca²⁺ and Co²⁺ had a significant activating effect on Bgl59, while the presence of 0.1% SDS resulted in a complete loss of enzyme activity. The presence of 0.10 mol/L glucose and 0.30 mol/L xylose increased the activity of Bgl59 by 74% and 91%, respectively. Moreover, the enzyme remained the relative activity above 50% even when being cultured with 1.25 mol/L glucose or 2.00 mol/L xylose. [Conclusion] Bgl59 exhibits outstanding enzymatic properties, robust pH stability, and tolerance to metal ions and chemical reagents. It is a rare glucose-activated β-glucosidase with exceptional tolerance to glucose, holding significant potential for future industrial production and application.