Cavities create a potential back door in epoxide hydrolase Rv1938 from Mycobacterium tuberculosis-A molecular dynamics simulation study

mesT, a unique epoxide hydrolase, is essential for optimal growth of Mycobacterium tuberculosis in the presence of styrene oxide

Aim: mesT of Mycobacterium tuberculosis, a hypothetical/putative epoxide hydrolase, is predicted to convert toxic epoxides to the more water-soluble and less toxic diols. Detailed characterization of the protein was carried out. Results: mesT demonstrated esterase as well as epoxide hydrolase activity. It was membrane bound and was upregulated under hypoxic conditions. The enzyme was able to degrade styrene oxide. The presence of antisense against this gene resulted in the inhibition of in vitro bacterial growth/survival in the presence of styrene oxide. Conclusion & future perspective: We demonstrated that mesT possessed epoxide hydrolase activity and styrene oxide might be its physiological substrate. Inhibition of mesT reduced the growth of the bacteria in presence of styrene oxide and its expression under hypoxic condition suggested its role in intracellular survival of bacteria.

Active-Site Flexibility and Substrate Specificity in a Bacterial Virulence Factor: Crystallographic Snapshots of an Epoxide Hydrolase

Pseudomonas aeruginosa secretes an epoxide hydrolase with catalytic activity that triggers degradation of the cystic fibrosis transmembrane conductance regulator (CFTR) and perturbs other host defense networks. Targets of this CFTR inhibitory factor (Cif) are largely unknown, but include an epoxy-fatty acid. In this class of signaling molecules, chirality can be an important determinant of physiological output and potency. Here we explore the active-site chemistry of this two-step α/β-hydrolase and its implications for an emerging class of virulence enzymes. In combination with hydrolysis data, crystal structures of 15 trapped hydroxyalkyl-enzyme intermediates reveal the stereochemical basis of Cif's substrate specificity, as well as its regioisomeric and enantiomeric preferences. The structures also reveal distinct sets of conformational changes that enable the active site to expand dramatically in two directions, accommodating a surprising array of potential physiological epoxide targets. These new substrates may contribute to Cif's diverse effects in vivo, and thus to the success of P. aeruginosa and other pathogens during infection.