Novel Potential Binding Sites for Selective Inhibitor Design of Human Soluble Epoxide Hydrolase

Abstract

Human soluble epoxide hydrolase (hsEH) has been known to be involved in the hydrolysis of epoxyeicosatrienoic acids (EETs), which are anti-inflammatory and cardioprotective signalling molecules. Since the conversion of EETs into the corresponding diols generates non-bioactive molecules, the enzyme’s inhibition would be beneficial. hsEH quickly became the molecular target, however, the proposed inhibitors directed toward this enzyme have not undergone clinical trials, mostly due to their low solubility in water. Our goal is to indicate new regions, distinct from those already investigated, that could be considered during the development of novel and perhaps more soluble inhibitors of hsEH. To fulfil this goal, we used a combination of classical and mixed-solvent molecular dynamics (cMD and MixMD) simulations and a ligand tracking approach. Such a strategy, considers conformational changes in the interior of the enzyme, extends conformational space of binding cavities, and provides insight into different sets of potential binding modes. By analysis of the local distribution of different molecular probes (water and organic cosolvent molecules), we were able to identify potential binding sites (hot-spots), which can indicate the location of the most important functional groups for the binding of designed inhibitors. The uniqueness of the binding spots was examined by superpositioning the indicated hot-spots with a map of chemical interactions between the known inhibitors and hsEH. We analysed all available crystal structures of hsEHs with inhibitors deposited in the PDB database to gain insight into the binding modes of the known inhibitors and to find similarities and dissimilarities between them. By comparing the results obtained based on the map of chemical interactions, with the regions identified by using cMD and MixMD, we were able to identify regions that have not been targeted by ligands until now and which are promising possible binding sites for polar groups that would be beneficial for inhibitors solubility.