X-ray Crystallography Deciphers the Activity of Broad-Spectrum Boronic Acid β-Lactamase Inhibitors

Abstract

Recent decades have witnessed a dramatic increase of multidrug resistant (MDR) bacteria, compromising the efficacy of available antibiotics, and a continual decline in the discovery of novel antibacterials. We recently reported the first library of benzo[b]thiophen-2-ylboronic acid inhibitors sharing broad spectrum activity against β-lactamases (BLs). The ability of these compounds to inhibit structurally and mechanistically different types of β-lactamases has been here structurally investigated. An extensive X-ray crystallographic analysis of boronic acids (BAs) binding to proteins representative of serine BLs (SBLs) and metallo β-lactamases (MBLs) have been conducted to depict the role played by the boronic group in driving molecular recognition, especially in the interaction with MBLs. Our derivatives are the first case of noncyclic boronic acids active against MBLs and represent a productive route toward potent broad-spectrum inhibitors.

4-Amino-1,2,4-triazole-3-thione as a Promising Scaffold for the Inhibition of Serine and Metallo-β-Lactamases

“…This often implies that a covalent mechanism of inhibition is involved, at least for SBLs [26,48]. In our case, the developed molecules possess a micromolar affinity towards SBLs and MBLs and were non-covalent inhibitors of SBLs.…”

“…The binding affinity K i was estimated from the determined IC 50 by Cheng-Prusoff equation as per competitive inhibition ( Table 1 and Table S1) [45]. For targeted enzyme a known, in house broad spectrum inhibitor, was used as control [26,28].…”

“…Among metallo-BLIs (MBLIs) so far designed, bisthiazolidines, thiols, tetrazoles, sulphonamides, succinic acids, hydroxamates, and boronic acids are recurrent moieties [11,[25][26][27][28][29]. In particular, sulfur-containing molecules that are able to interfere, in the binding site, with the hydrolytic water and the Zn-ion network of interactions represent chemical entities that have been widely characterized as MBLIs.…”

Targeting the Class A Carbapenemase GES-5 via Virtual Screening

“…Thirteen crystal structures of GES-type BLs are now available, making it an attractive target for the structure-based design of novel molecules able to counteract antibiotic resistance mediated by these enzymes [12][13][14][15][16][17][18]. However, compared to other carbapenemases, the number of available GEStype BL crystal structures is still quite limited, reflecting the low level of attention so far dedicated to the GES family.…”

“…However, compared to other carbapenemases, the number of available GEStype BL crystal structures is still quite limited, reflecting the low level of attention so far dedicated to the GES family. For GES-5, the target of our study, five crystal structures of the wild-type or mutant enzyme have been deposited in the Protein Data Bank (PDB) [12][13][14]. Two of them are binary complexes with either the substrate imipenem or a boronic acid inhibitor.…”