Inhibitor Screening Of Target Enzymes Based On The Structures Of FabI From Salmonella And GlmU From Xanthomonas

Traditional drug discovery and development need a huge amount of money and a long period; furthermore, the success rates for obtaining useful drugs were very low. With the development of computer-aided drug design, the capital investment in drug design was decreased remarkably, and the aimlessness and occasionlity was reduced, moreover, the research and development period was shortened dramatically. In this study, inhibitor screening of target enzymes based on the structures of enoyl-ACP reductase (ENR) from Salmonella enterica and N-Acetylglucosamine-1-phosphate uridyltransferase (GlmU) from Xanthomonas oryzae pv. oryzae were carried out by computer-aided drug design method.As a major cause of food-borne disease, S. enter ica is a major public health concern worldwide. Fatty acid biosynthesis (FAS) is indispensable in bacterial membrane biosynthesis. ENRs, catalyzing the key reaction in FAS, have been proved to be an attractive target in drug design. In this study, structure-based screening of potential inhibitors for ENR from S. enteritic (SeFabI) was carried out. Luteolin, a traditional Chinese medicine monomer, was selected and proven to be an inhibitor of SeFabI with the IC50 of 15.6±0.5μmol/L. The inhibitory kinetics results showed that luteolin was an uncompetitive inhibitor of crotonyl-CoA with the inhibition constant(Ki) of 15.1±0.3μmol/L. Three mutants SeFabI[G93V], SeFabI[G93S], and SeFabI[Y156F] were designed to investigate the interaction mechanism between the inhibitor and SeFabI target. The results revealed that specific activities and substrate affinities of SeFabI[G93V] and SeFabI[G93S] were extremely similar to wild-type SeFabI, while SeFabI[Y156F] lost the substrate catalytic activity. On the other hand, SeFabI[G93V] showed high level resistances for both luteolin and triclosan. Interestingly, the SeFabI[G93S] mutation showed luteolin sensitivity but triclosan resistence. Luteolin, as a Chinese medicine monomer with high security and efficiency, would be able to develop as a lead compound for combating resistant bacteria.Bacterial leaf blight caused by X. oryzae pv. oryzae is one of the most serious diseases of rice causing high yield losses worldwide. The reports about glmU gene knockout proved that GlmU is a crucial enzyme in the biosynthesis of cell wall and therefore an attractive target for antibiotic drug discovery. The results in this study displayed that the Gly13, Arg17, Lys24 and Asp 105 are key residues in the uridyltransferase catalytic activity. According to these results, the structure-based screening of potential inhibitors for GlmU from X. oryzae pv. oryzae (XooGlmU) was performed. With the biological activity testing,4 compounds were identified as specific inhibitors for XooGlmU with IC50 in the 0.5-10μmol/L range. The inhibitory kinetics results showed that all of them were competitive inhibitors of the substrate GlcNAc-1-P and uncompetitive inhibitors of UTP with the minimum Ki of 0.2μmol/L. More importantly, the compounds 3 and 4 showed obvious bacteriocidal properties against X. oryzae pv. oryzae with MIC values of 75 and 50μg/mL, respectively. This is the first time that we obtain the compounds which not only suppress the GlmU but also have the bacteriocidal properties. These molecules provide novel chemical scaffolds for future GlmU antimicrobial drug discovery.