Metallo-β-Lactamases: A Major Threat to Human Health (original) (raw)
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Frontiers in Chemistry
β-Lactams are the most widely employed antibiotics in clinical settings due to their broad efficacy and low toxicity. However, since their first use in the 1940s, resistance to β-lactams has proliferated to the point where multi-drug resistant organisms are now one of the greatest threats to global human health. Many bacteria use β-lactamases to inactivate this class of antibiotics via hydrolysis. Although nucleophilic serine-β-lactamases have long been clinically important, most broad-spectrum β-lactamases employ one or two metal ions (likely Zn2+) in catalysis. To date, potent and clinically useful inhibitors of these metallo-β-lactamases (MBLs) have not been available, exacerbating their negative impact on healthcare. MBLs are categorised into three subgroups: B1, B2, and B3 MBLs, depending on their sequence similarities, active site structures, interactions with metal ions, and substrate preferences. The majority of MBLs associated with the spread of antibiotic resistance belong...
The Development of New Small-Molecule Inhibitors Targeting Bacterial Metallo-β-lactamases
Current topics in medicinal chemistry, 2018
Metallo-β-lactamases (MBLs) are a family of Zn(II)-dependent enzymes that can hydrolyze almost allβ-lactam antibiotics. Horizontal transferofthe genes encodingMBLsamong Gram-negative bacteria pathogens has led to the emergence of extensively drug-resistantpathogens, which now represent a major threat to human health.As there is not to date yet a clinicallyavailable MBL inhibitor, the discovery of new MBL inhibitors has great urgency. This review highlights the recent developments in the discovery of small-molecule MBL inhibitors.
Metallo-β-lactamase structure and function
Annals of the New York Academy of Sciences, 2012
β-lactam antibiotics are the most commonly used antibacterial agents and growing resistance to these drugs is a concern. Metallo-β-lactamases are a diverse set of enzymes that catalyze the hydrolysis of a broad range of β-lactam drugs including carbapenems. This diversity is reflected in the observation that the enzyme mechanisms differ based on whether one or two zincs are bound in the active site which, in turn, is dependent on the subclass of β-lactamase. The dissemination of the genes encoding these enzymes among Gram-negative bacteria has made them an important cause of resistance. In addition, there are currently no clinically available inhibitors to block metallo-β-lactamase action. This review summarizes the numerous studies that have yielded insights into the structure, function, and mechanism of action of these enzymes.
Overcoming differences: The catalytic mechanism of metallo-β-lactamases
FEBS letters, 2015
Metallo-β-lactamases are the latest resistance mechanism of pathogenic and opportunistic bacteria against carbapenems, considered as last resort drugs. The worldwide spread of genes coding for these enzymes, together with the lack of a clinically useful inhibitor, have raised a sign of alarm. Inhibitor design has been mostly impeded by the structural diversity of these enzymes. Here we provide a critical review of mechanistic studies of the three known subclasses of metallo-β-lactamases, analyzed at the light of structural and mutagenesis investigations. We propose that these enzymes present a modular structure in their active sites that can be dissected into two halves: one providing the attacking nucleophile, and the second one stabilizing a negatively charged reaction intermediate. These are common mechanistic elements in all metallo-β-lactamases. Nucleophile activation does not necessarily requires a Zn(II) ion, but a Zn(II) center is essential for stabilization of the anionic i...
Metallo-β-Lactamase Inhibitors Inspired on Snapshots from the Catalytic Mechanism
Biomolecules, 2020
β-Lactam antibiotics are the most widely prescribed antibacterial drugs due to their low toxicity and broad spectrum. Their action is counteracted by different resistance mechanisms developed by bacteria. Among them, the most common strategy is the expression of β-lactamases, enzymes that hydrolyze the amide bond present in all β-lactam compounds. There are several inhibitors against serine-β-lactamases (SBLs). Metallo-β-lactamases (MBLs) are Zn(II)-dependent enzymes able to hydrolyze most β-lactam antibiotics, and no clinically useful inhibitors against them have yet been approved. Despite their large structural diversity, MBLs have a common catalytic mechanism with similar reaction species. Here, we describe a number of MBL inhibitors that mimic different species formed during the hydrolysis process: substrate, transition state, intermediate, or product. Recent advances in the development of boron-based and thiol-based inhibitors are discussed in the light of the mechanism of MBLs...
Metallo-β-lactamases and a tug-of-war for the available zinc at the host–pathogen interface
Current Opinion in Chemical Biology, 2022
Metallo-b-lactamases (MBLs) are zinc-dependent hydrolases that inactivate virtually all b-lactam antibiotics. The expression of MBLs by Gram-negative bacteria severely limits the therapeutic options to treat infections. MBLs bind the essential metal ions in the bacterial periplasm, and their activity is challenged upon the zinc starvation conditions elicited by the native immune response. Metal depletion compromises both the enzyme activity and stability in the periplasm, impacting on the resistance profile in vivo. Thus, novel inhibitory approaches involve the use of chelating agents or metal-based drugs that displace the native metal ion. However, newer MBL variants incorporate mutations that improve their metal binding abilities or stabilize the metal-depleted form, revealing that metal starvation is a driving force acting on MBL evolution. Future challenges require addressing the gap between in cell and in vitro studies, dissecting the mechanism for MBL metalation and determining the metal content in situ.
bioRxiv (Cold Spring Harbor Laboratory), 2018
Metallo--lactamase (MBL)-producing Enterobacteriaceae are of grave clinical concern, particularly as there are no metallo--lactamase inhibitors approved for clinical use. The discovery and development of MBL inhibitors to restore the efficacy of available -lactams are thus imperative. We investigated a zinc-chelating moiety, 1,4,7triazacyclononane (TACN), for its inhibitory activity against clinical carbapenem-resistant Enterobacteriaceae. MICs, minimum bactericidal concentrations (MBCs), the serum effect, fractional inhibitory concentration indexes, and time-kill kinetics were determined using broth microdilution techniques according to Clinical and Laboratory Standards Institute (CSLI) guidelines. Enzyme kinetic parameters and the cytotoxic effects of TACN were determined using spectrophotometric assays. The interactions of the enzyme-TACN complex were investigated by computational studies. Meropenem regained its activity against carbapenemase-producing Enterobacteriaceae, with the MIC decreasing from between 8 and 64 mg/liter to 0.03 mg/liter in the presence of TACN. The TACNmeropenem combination showed bactericidal effects with an MBC/MIC ratio of Յ4, and synergistic activity was observed. Human serum effects on the MICs were insignificant, and TACN was found to be noncytotoxic at concentrations above the MIC values. Computational studies predicted that TACN inhibits MBLs by targeting their catalytic activesite pockets. This was supported by its inhibition constant (K i), which was 0.044 M, and its inactivation constant (K inact), which was 0.0406 min Ϫ1 , demonstrating that TACN inhibits MBLs efficiently and holds promise as a potential inhibitor. IMPORTANCE Carbapenem-resistant Enterobacteriaceae (CRE)-mediated infections remain a significant public health concern and have been reported to be critical in the World Health Organization's priority pathogens list for the research and development of new antibiotics. CRE produce enzymes, such as metallo--lactamases (MBLs), which inactivate -lactam antibiotics. Combination therapies involving a -lactam antibiotic and a -lactamase inhibitor remain a major treatment option for infections caused by -lactamase-producing organisms. Currently, no MBL inhibitor--lactam combination therapy is clinically available for MBL-positive bacterial infections. Hence, developing efficient molecules capable of inhibiting these enzymes could be a promising way to overcome this phenomenon. TACN played a significant role in the inhibitory activity of the tested molecules against CREs by potentiating the activity of carbapenem. This study demonstrates that TACN inhibits MBLs efficiently and holds promises as a potential MBL inhibitor to help curb the global health threat posed by MBL-producing CREs.
Metallo-β-lactamases withstand low Zn(II) conditions by tuning metal-ligand interactions
Nature Chemical Biology, 2012
A number of multiresistant bacterial pathogens inactivate antibiotics by producing Zn II-dependent β-lactamases. We show that metal uptake leading to an active dinuclear enzyme in the periplasmic space of Gram-negative bacteria is ensured by a cysteine residue, an unusual metal ligand in oxidizing environments. Kinetic, structural and affinity data show that such Zn II-Cys interaction is an adaptive trait tuning the metal binding affinity, thus enabling antibiotic resistance at restrictive Zn II concentrations. The efficacy of β-lactam antibiotics is being challenged by the worldwide dissemination of genes encoding metallo-β-lactamases (MβLs). 1, 2 These hydrolases are able to confer multiresistance to β-lactam antibiotics in many pathogenic and opportunistic bacteria, leading to an urgent need for MβL inhibitors or new generations of β-lactam antibiotics. Most of the clinically relevant targets are in mobile genetic elements and belong to subclass B1. 2 These enzymes bind up to two Zn II equivalents, giving rise to a tetrahedral site (M1), with 3 His and a bridging hydroxide (the nucleophile in the hydrolysis reaction) as metal ligands, and a trigonal-bypiramidal site (M2), with a Cys, His and Asp ligand set, completed by two solvent molecules. 3, 4 Assessing the mechanistic role and essentiality of the M1 and Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use: