Discovery of a compound which acts as a bacterial UMP kinase PyrH inhibitor

PyrH is a member of the UMP kinase family that catalyses the conversion of UMP to UDP, an essential step in the pyrimidine metabolic pathway in a variety of bacteria including those causing community-acquired respiratory tract infections (RTIs). In this study, we have developed a luminescence-based kinase assay of PyrH and evaluated the inhibitory activity of PYRH-1 (sodium {3-[4-tert-butyl-3-(9H-xanthen-9-ylacetylamino)phenyl]-1-cyclohexylmethylpropoxycarbonyloxy}acetate). PYRH-1 inhibits PyrH derived from both Streptococcus pneumoniae and Haemophilus influenzae with IC50 (concentration of inhibitor giving a 50% decrease in enzyme activity) values of 48 and 75 similar to mu M, respectively, whose inhibitory activity against S.similar to pneumoniae PyrH was far higher compared with that of UTP (IC50 similar to=similar to 710 similar to mu M), an allosteric PyrH inhibitor. The molecular interaction analysis by surface plasmon resonance suggested that PYRH-1 directly interacts with S.similar to pneumoniae PyrH at one-to-one molar ratio. Finally, PYRH-1 was shown to have antimicrobial activity against several different bacteria causing RTIs, such as S.similar to pneumoniae, Staphylococcus aureus, H.similar to influenzae (acrA knockout strain), suggesting that PYRH-1 is a prototype chemical compound that can be harnessed as an antimicrobial drug with a novel mode of action by targeting bacterial PyrH.