An Investigation of the Interaction of Co-Solvent With Substrates In the Pig Liver Esterase-Catalyzed Hydrolysis of Malonate Esters

Previously, we have reported the effect of several co-solvents, including ethanol, on the enantioselective outcome of pig liver esterase (PLE) hydrolysis reactions. The greatest improvements were observed in those substrates that contained an atom capable of forming a hydrogen bond in the sidechain portion of the molecule. To further explore the interaction between substrate and ethanol, a second series of substrates were synthesized, in which the hydrogen bonding atoms of the side chain were modified, and subjected to PLE hydrolysis. Substrates containing atoms capable of forming hydrogen bonds showed the largest equilibrium constants. However, a large equilibrium constant did not always produce significant changes in enantioselectivity as hypothesized. Finally, molecular modeling experiments were performed to obtain a better understanding of the interactions. These experiments revealed that there are substrate–enzyme interactions that can be influenced by the addition of ethanol