Enolase is a glycolytic metalloenzyme involved in carbon metabolism. The advantage of targeting enolase lies in its essentiality in many biological processes such as cell wall formation, RNA turnover and as a plasminogen receptor. We initially used a DARTS assay to identify enolase as a target in Escherichia coli. The antibacterial activity of α-, β-, and γ-substituted seven-member ring tropolones were first evaluated against four strains representing a range of Gram-negative bacteria. We observed that the chemical properties and position of the substituents on the tropolone ring plays an important role in the biological activity of the investigated compounds. Both αand βsubstituted phenyl derivatives of tropolone were the most active with MIC values in the range of 11-14μg/mL. The potential inhibitory activity of the synthetic tropolones was further evaluated using an enolase inhibition assay, X-ray crystallography and molecular docking simulations. The catalytic activity of enolase was effectively inhibited by both the naturally occurring p-thujaplicin and αand βsubstituted phenyl derivatives of tropolones with IC 50 values in range of 8 to 11 μM. Ligand binding parameters were assessed by ITC and DSC techniques and agreed with the in vitro data. Our studies validate the antibacterial potential of tropolones with careful consideration of position and character of chelating moieties for stronger interaction with metal ions and residues in the enolase active site.

Human herpesviruses (HHVs) establish lifelong latent infections, which undergo periodic reactivation and remain a major cause of morbidity and mortality, especially in immunocompromised individuals. Currently, HHV infections are treated primarily with agents that target viral DNA polymerase, including nucleoside analogs; however, long-term treatment can be complicated by the development of drug resistance.

Many years ago, the natural secondary metabolite SF2312, produced by the actinomycete Micromonospora, was reported to display broad spectrum antibacterial properties against both Gram-positive and Gram-negative bacteria. Recent studies have revealed that SF2312, a natural phosphonic acid, functions as a potent inhibitor of human enolase. The mechanism of SF2312 inhibition of bacterial enolase and its role in bacterial growth and reproduction, however, have remained elusive. In this work, we detail a structural analysis of E. coli enolase bound to both SF2312 and its oxidized imide-form. Our studies support a model in which SF2312 acts as an analog of a high energy intermediate formed during the catalytic process. Biochemical, biophysical, computational and kinetic characterization of these compounds confirm that altering features characteristic of a putative carbanion (enolate) intermediate significantly reduces the potency of enzyme inhibition. When SF2312 is combined with fosfomycin in the presence of glucose-6 phosphate, significant synergy is observed. This suggests the two agents could be used as a potent combination, targeting distinct cellular mechanism for the treatment of bacterial infections. Together, our studies rationalize the structure-activity relationships for these phosphonates and validate enolase as a promising target for antibiotic discovery.

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In the cation of the title mol­ecular salt, C18H13N4O+·Cl−·H2O, the dihedral angle between the mean planes of the 1,10-phenanthroline system and the phenol ring is 14.40 (19)°. The crystal packing is stabilized by O—H⋯O hydrogen bonds, weak N—H⋯Cl and O—H⋯Cl inter­molecular inter­actions and π—π stacking inter­actions [centroid–centroid distance = 3.6944 (13) and 3.9702 (12) Å]