Studies of PurE from Bacillus anthracis: Its Solution Properties and Inhibitors

To combat antibacterial drug resistance, a study of a bacterial enzyme (PurE) of the de novo purine biosynthetic pathway was carried out for antimicrobial agent development. Thermal shift method for high-throughput screening of compounds binding to PurE from Bacillus anthracis was optimized which included using low ionic strength condition to accentuate the degree of thermal stabilization. Identified leads were further selected by computation docking followed by UV-based enzymatic activity assay to identify inhibitory compounds. Excellent minimum inhibitory concentration (MIC), 0.05–0.15 lg/mL, was determined for several compounds against Bacillus anthracis (∆ANR strain), Escherichia coli (BW25113 strain, wild-type and ∆TolC-), Francisella tularensis, Staphylococcus aureus (both methicillin susceptible and methicillin-resistant strains) and Yersinia pestis. It was identified that the compounds with low MIC values shared a common core structure. The results suggest that another enzyme(s) is targeted by the identified compounds as shown by the difference in concentration for enzyme inhibition and MIC. Solution property of PurE was studied by circular dichroism, UV-based enzymatic assay, tryptophan quenching, and chemical unfolding in low to high ionic strength condition to better understand enzyme’s local conformation and activity for further antimicrobial agent development.