Computationally driven rational design of substrate promiscuity on serine ester hydrolases

Abstract

Enzymes with a broad substrate specificity are of great interest both at the basic and applied level. Understanding the main parameters that make an enzyme substrate ambiguous could be thus important not only for their selection from the ever-increasing amount of sequencing data but also for engineering a more substrate promiscuous variant. This issue, which remains unresolved, was herein investigated by targeting a serine ester hydrolase (EH102), which exhibits a narrow substrate spectrum, being only capable of hydrolyzing 16 out of 96 esters tested. By using a modeling approach, we demonstrated that one can rationalize active site parameters defining substrate promiscuity, and that based on them the substrate specificity can be significantly altered. This was accomplished by designing two variants, EH102DM2 and EH102TM2, that hydrolyze 51 and 63 esters, respectively, while maintaining similar or higher turnover rates compared to the original enzyme. We hypothesized that the parameters identified here (the volume, size, exposure, enclosure, hydrophobicity, and hydrophilicity of the active site cavity and its tightness) can serve in the future to expand the substrate spectra of esterases and thus expand their use in biotechnology and synthetic chemistry.