The role of aromatic residue W20 in the activity and enantioselectivity control of esterase BioH toward aryl substrate

• π–π Interaction between W20 and substrate affects the catalytic performance of BioH.
• Mutation of W20 into Ala or Val led to complete loss of activity.
• Mutation of W20 into Phe had little effect on the activity and enantioselectivity.
• Mutation of W20 affected the interactions between the active sites and substrate.

Aromatic π–π stacking interaction plays an important role in the enzyme-ligand recognition and stabilization. Esterase BioH, an α/β hydrolase from Escherichia coli, exhibited potential in the chiral synthesis of alcohols and aryl prochiral diesters. In the present work, the influence of aromatic residue W20 on the activity and enantioselectivity of BioH toward aryl substrate was investigated. Mutation of Trp into Ala or Val led to complete loss of activity, while replacement of Trp by Phe had little effect on the activity and enantioselectivity. Structural and energetic analysis demonstrated that π–π stacking interactions were formed between the residue W20 and the substrate, as well as the residues W20 and F141, which facilitated the stabilization of substrate at the transition state. Moreover, the different probabilities of the parallel–shifted stacking interaction between the residue 20 and R-/S-enantiomer were found related to the enantioselectivity. Thus, it could be concluded that the π–π stacking interaction between the residue W20 and the substrate was crucial in the determination of enzymatic catalytic performance. The results not only deepened our understanding in the catalytic mechanism of BioH, but also facilitated further enzyme redesign.

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