Inhibition of Metallo-beta-lactamases inspired by snapshots of the catalytic mechanism

ALEJANDRO J. VILA; ROSSI, MA. AGUSTINA; BAHR, GUILLERMO; DOTTA, GINA; DELMONTI, JULIANA; LÓPEZ, CAROLINA; CARNEVALE, MATÍAS; PARODI, CLARISA; TOMATIS, PABLO E; GONZALEZ, LISANDRO J

Montevideo

Conferencia; 7th Latin American Conference on Biological Inorganic Chemistry; 2021

LABIC

Metallo-beta-lactamases (MBLs) are Zn(II)-dependent beta-lactamases that constitute the latest resistance mechanism of pathogenic and opportunistic bacteria against carbapenems, considered as last resort drugs. MBLs display a broad substrate profile, being capable of inactivating also penicillins and cephalosporins. Furthermore, these enzymes are refractory to the action of all currently available beta-lactamase inhibitors. MBLs are becoming increasingly widespread in clinically relevant Gram-negative pathogens.MBLs are classified into three subclasses, with diverse active site topologies, metal coordination environment and Zn(II) stoichiometry. This diversity has hampered the development of an efficient pan-MBL inhibitor. As a result, the use of chelating compounds as MBL inhibitors has been pursued, despite the risk of off-target activity arising from indiscriminate chelation of metal ions.One strategy to address the challenge of MBL inhibition is to exploit knowledge of common features of beta-lactam antibiotic binding and hydrolysis that are shared by different MBLs despite their structural differences. We have pursued a combined kinetic, spectroscopic and structural study of the mechanism of carbapenem hydrolysis by MBLs. MBLs of the multiple subtypes have been shown to hydrolyze carbapenems via a common catalytic intermediate, in which the beta-lactam ring has already been cleaved, that interacts with the metal site in a manner that is consistent across different enzyme targets. The binding mode of these intermediates resembles that reported for several enzyme-product adducts described by X-ray crystallography.Based on this approach, we have developed a series of inhibitors: bisthiazolidines (BTZs), bicyclic substrate mimics decorated with a zinc-binding thiol moiety, that are cross-class MBL inhibitors active in vitro and against bacterial pathogens expressing MBLs, and 2-mercaptomethyl-thiazolidines (MMTZs), a that partially resemble MBL-bound intermediates and product species, whilst retaining the metal-binding thiol group present in the BTZs. These compounds target MBLs from all subclasses and are able to restore the efficacy of carbapenems against clinical strains expressing MBLs