Exploring the catalytic mechanism of a novel β-glucosidase BGL0224 from Oenococcus oeni SD-2a: Kinetics, spectroscopic and molecular simulation

The β-glucosidase derived from microorganisms has attracted worldwide interest for their industrial applications, but studies on β-glucosidases from Oenococcus oeni are rare. In this paper, catalytic mechanism of a novel β-glucosidase BGL0224 of Oenococcus oeni SD-2a was explored for the first time by kinetic parameters determination, fluorescence spectroscopy and quenching mechanism analysis, molecular dynamics simulation. The results indicated that BGL0224 had universal catalytic effect on different types of glycoside substrates, but the catalytic efficiencies were different. Fluorescence quenching analysis results suggested that the quenching processes between BGL0224 and seven kinds of substrates were predominated by the static quenching mechanism. A reasonable three-dimensional model of BGL0224 was obtained using the crystal structure of E.coli BglA as a template. The analysis results of molecular simulation (RMSD, Rg, RMSF and hydrogen bonding) showed that the composite system ‘BGL0224-pNPG’ was very stable after 40 ns. The catalytic process of BGL0224 acting on ‘p-Nitrophenyl β-d-glucopyranoside’ conformed to the double displacement mechanism. Two glutamic acid residues ‘Glu178 and Glu377’ played a vital role in the whole catalytic process. Overall, this study gave specific insights on the catalytic mechanism of BGL0224, which was of great significance for developing its potential applications in food industry.