Spectroscopic and in silico investigation of the interaction between GH1 β-glucosidase and ginsenoside Rb1

The function and application of beta-glucosidase attract attention nowadays. beta-glucosidase was confirmed of transforming ginsenoside Rb-1 to rare ginsenoside, but the interaction mechanism remains not clear. In this work, beta-glucosidase from GH1 family of Paenibacillus polymyxa was selected, and its gene sequence bglB was synthesized by codon. Then, recombinant plasmid was transferred into Escherichia coli BL21 (DE3) and expressed. The UV-visible spectrum showed that ginsenoside Rb-1 decreased the polarity of the corresponding structure of hydrophobic aromatic amino acids (Trp) in beta-glucosidase and increased new pi-pi* transition. The fluorescence quenching spectrum showed that ginsenoside Rb-1 inhibited intrinsic fluorescence, formed static quenching, reduced the surface hydrophobicity of beta-glucosidase, and K-SV was 8.37 x 10(3) L/M (298K). Circular dichroism (CD) showed that secondary structure of beta-glucosidase was changed by the binding action. Localized surface plasmon resonance (LSPR) showed that beta-glucosidase and Rb-1 had strong binding power which KD value was 5.24 x 10(-4) (+/- 2.35 x 10(-5)) M. Molecular docking simulation evaluated the binding site, hydrophobic force, hydrogen bond, and key amino acids of beta-glucosidase with ginsenoside Rb-1 in the process. Thus, this work could provide basic mechanisms of the binding and interaction between beta-glucosidase and ginsenoside Rb-1.