Mycobacterial Epoxide Hydrolase EphD Is Inhibited by Urea and Thiourea Derivatives

The genome of the human intracellular pathogen Mycobacterium tuberculosis encodes an unusually large number of epoxide hydrolases, which are thought to be involved in lipid metabolism and detoxification reactions needed to endure the hostile environment of host macrophages. These enzymes therefore represent suitable targets for compounds such as urea derivatives, which are known inhibitors of soluble epoxide hydrolases. In this work, we studied in vitro the effect of the thiourea drug isoxyl on six epoxide hydrolases of M. tuberculosis using a fatty acid substrate. We show that one of the proteins inhibited by isoxyl is EphD, an enzyme involved in the metabolism of mycolic acids, key components of the mycobacterial cell wall. By analyzing mycolic acid profiles, we demonstrate the inhibition of EphD epoxide hydrolase activity by isoxyl and two other urea-based inhibitors, thiacetazone and AU1235, inside the mycobacterial cell.