Structural analysis and insights into the glycon specificity of the rice GH1 Os7BGlu26 β-D-mannosidase

The structures of rice Os7BGlu26 β-D-mannosidase, of its product complex with β-D-mannose and of Os7BGlu26 computationally docked with 4-nitrophenyl β-D-mannoside suggest that the D-­mannose pyranose ring makes a conformational transition from ^OS₂ skew boat to B_2,5 boat to ¹S₅ skew boat during the deglycosylation of the enzyme in hydrolysis. These structures led to the hypothesis that the residues interacting with the catalytic acid/base play a role in determining β-D-mannosidase activity, which was supported by site-directed mutagenesis and kinetic analysis.