The secrets of biocatalysis: adaptation of epoxide hydrolase enzyme from Bacillus megaterium for drug synthesis

Abstract

Since the beginning of life, it can be found in Nature biomolecules that make all the chemical reactions necessary for life. These biomolecules known as enzymes are indeed the most efficient, specific and selective catalyst known. This has led to biocatalysis, the use of enzymes to catalyse the transformation of organic compounds. Despite the great advantages, there are lots of reactions of industrial interest that cannot be carried out with high efficiencies by natural enzymes. This has led to enzyme engineering, whose job is to modify and apply laboratory evolved enzymes for new purposes for which they were not originally designed. As mentioned above, enzymes found in Nature usually do not reach the requirements of pharmaceutical and fine chemical industries. In some cases, it may be due to its low regioselectivity and enantioselectivity towards non-natural substrates of industrial interests. In others, it may be caused by the narrow substrate scope of the WT enzyme, which, for example, does not allow the bioresolution of bulky substrates. This could be one of the main drawbacks related to epoxide hydrolases (EHs) enzyme of Bacillus megaterium (BmEH), the enzyme of interest in this research work. BmEH enzyme shows activity towards bulky substrates, such as naphthyl glycidyl ether (NGE) (valuable precursor of propranolol beta blocker drug), but nevertheless its efficiency is worse compared to those observed by the natural phenyl glycidyl ether (PGE) substrate. In general, EHs are a type of enzymes belonging to the a,b-hydrolase family that are able of performing selective asymmetric epoxide hydrations. In particular, BmEH catalyses the opening of the epoxide ring of the (R)-enantiomer of the PGE, leaving the (S) enantiomer ideally unreacted, which is interesting because the (S) enantiomer is a valuable intermediate beta-blocker of the alprenolol drug. Although the general mechanism of EHs is currently known, details of processes that occur before (substrate binding) and/or after (product release) are not yet known. For this reason, the aim of this study is to understand the conformational dynamics of the BmEH natural enzyme in the presence of each enantiomer of PGE (BmEH – (R/S)-PGE system) through Molecular Dynamic (MD) simulations