Enhancing the enantioselectivity of CALB by substrate imprinting: A combined experimental and molecular dynamics simulation model study

International audienceKinetic resolution of pentan-2-ol by CALB catalyzed enantioselective transesterification, with various alkyl-propanoate acyl donors, was studied in a solid-gas reactor. Results show that the leaving alkoxy group influences the enantiomeric ratio of the reaction. Resolution of pentan-2-ol with methyl propanoate gives an enantiomeric ratio of 62. Esters with longer linear alkyl chains, from ethyl to pentyl propanoate give higher enantiomeric ratios, comprised between 103 and 117. Enantiopure ester (R)-1-methylpentyl propanoate increases the enantiomeric ratio to 140 compared with E = 120 for the racemic mixture. In contrast, enantiopure (S)-1-methylpentyl propanoate decreases the enantiomeric ratio to 72. Our data support the notion of an imprinting effect or "ligand-induced enzyme memory" caused by the shape of the leaving alcohol. To simulate the imprinting effect caused by the alkoxy part of the acyl donor, molecular modeling studies were performed with both (R)- and (S)- enantiopure 1-methylpentyl propanoate. To investigate how the first step of the reaction, through the first tetrahedral intermediate, affects the enzyme conformation depending on the enantiopure ester substrate used, 20 ns molecular dynamics simulations were carried out. Clustering analysis was done to study relevant conformations of the systems. Differences in the global conformation of the enzyme between systems with R or S enantiomers were not observed. Interestingly however, orientation of the partially buried side chain for Ile285 was affected. This could explain the increased enantiomeric ratio observed with the substrate ester (R)-1-methylpentyl propanoate due to an improved (R)-pentan-2-ol/enzyme interaction