QM/MM Calculations Reveal the Molecular Origin of Stereodivergence in a CALB-Catalyzed Transacylation.

Stereodivergence is an important method in biocatalysis to access all possible stereoisomers by performing minimal changes in the enzymatic system. However, the growth remains slow due to an incomplete understanding of the role of mutations. Herein, we utilize an array of computational approaches, including MD simulations, DFT-based QM/MM calculations, and interaction energy profiling, to understand the origin of stereodivergence in a CALB-catalyzed transacylation reaction. As a proof of concept, we show the utility of transition state modeling in understanding the precise role of mutations in generating chiral switches and modulating the formation of stereoisomers by altering the substrate environment and active site dynamics. Electrostatics and interaction networks within the protein matrix play pivotal roles in determining stereoselectivity. These findings provide valuable mechanistic insights into enzyme-mediated stereodivergence and offer a framework for the rational design of highly selective biocatalysts in asymmetric catalysis.