Identification and molecular characterization of a psychrophilic GH1 β-glucosidase from the subtropical soil microorganism Exiguobacterium sp. GXG2

The products of bacterial β-glucosidases with favorable cold-adapted properties have industrial applications. A psychrophilic β-glucosidase gene named bglG from subtropical soil microorganism Exiguobacterium sp. GXG2 was isolated and characterized by function-based screening strategy. Results of multiple alignments showed that the derived protein BglG shared 45.7% identities with reviewed β-glucosidases in the UniProtKB/Swiss-Prot database. Functional characterization of the β-glucosidase BglG indicated that BglG was a 468 aa protein with a molecular weight of 53.2 kDa. The BglG showed the highest activity in pH 7.0 at 35 °C and exhibited consistently high levels of activity within low temperatures ranging from 5 to 35 °C. The BglG appeared to be a psychrophilic enzyme. The values of K(m), V(max), k(cat), and k(cat)/K(m) of recombinant BglG toward ρNPG were 1.1 mM, 1.4 µg/mL/min, 12.7 s(−1), and 11.5 mM/s, respectively. The specific enzyme activity of BglG was 12.14 U/mg. The metal ion of Ca(2+) and Fe(3+) could stimulate the activity of BglG, whereas Mn(2+) inhibited the activity. The cold-adapted β-glucosidase BglG displayed remarkable biochemical properties, making it a potential candidate for future industrial applications.