scholarly journals Impaired Inhibition by Avibactam and Resistance to the Ceftazidime-Avibactam Combination Due to the D179Y Substitution in the KPC-2 β-Lactamase

2017 ◽  
Vol 61 (7) ◽  
Author(s):  
Fabrice Compain ◽  
Michel Arthur
Keyword(s):  
Catalytic Properties ◽  
Residual Activity ◽  
Underlying Mechanism ◽  
Content Type ◽  
Y Substitution ◽  
Therapeutic Alternatives ◽  
Emergence Of Resistance ◽  
Hydrolysis Of ◽  
Insight Into

ABSTRACT The ceftazidime-avibactam antibiotic combination was recently shown to be at risk for the emergence of resistance under treatment. To gain insight into the underlying mechanism, we have analyzed the catalytic properties of a Klebsiella pneumoniae carbapenemase type 2 (KPC-2) β-lactamase harboring the D179Y substitution. We show that impaired inhibition by avibactam combined with significant residual activity for ceftazidime hydrolysis accounts for the resistance. In contrast, the D179Y substitution abolished the hydrolysis of aztreonam and imipenem, indicating that these drugs might provide therapeutic alternatives.

scholarly journals Peptidoglycan Cross-Linking in Glycopeptide-Resistant Actinomycetales

2014 ◽  
Vol 58 (3) ◽  
pp. 1749-1756 ◽  
Author(s):  
Jean-Emmanuel Hugonnet ◽  
Nabila Haddache ◽  
Carole Veckerlé ◽  
Lionel Dubost ◽  
Arul Marie ◽  
...  
Keyword(s):  
Streptomyces Coelicolor ◽  
Residual Activity ◽  
Resistance Mechanisms ◽  
Strain Atcc ◽  
Glycopeptide Resistance ◽  
Content Type ◽  
Peptidoglycan Structure ◽  
Cross Links ◽  
Acyl Donors ◽  
Hydrolysis Of

ABSTRACTSynthesis of peptidoglycan precursors ending ind-lactate (d-Lac) is thought to be responsible for glycopeptide resistance in members of the orderActinomycetalesthat produce these drugs and in related soil bacteria. More recently, the peptidoglycan of several members of the orderActinomycetaleswas shown to be cross-linked byl,d-transpeptidases that use tetrapeptide acyl donors devoid of the target of glycopeptides. To evaluate the contribution of these resistance mechanisms, we have determined the peptidoglycan structure ofStreptomyces coelicolorA(3)2, which harbors avanHAXgene cluster for the production of precursors ending ind-Lac, andNonomuraeasp. strain ATCC 39727, which is devoid ofvanHAXand produces the glycopeptide A40296. Vancomycin retained residual activity againstS. coelicolorA(3)2 despite efficient incorporation ofd-Lac into cytoplasmic precursors. This was due to ad,d-transpeptidase-catalyzed reaction that generated a stem pentapeptide recognized by glycopeptides by the exchange ofd-Lac ford-Ala and Gly. The contribution ofl,d-transpeptidases to resistance was limited by the supply of tetrapeptide acyl donors, which are essential for the formation of peptidoglycan cross-links by these enzymes. In the absence of a cytoplasmic metallo-d,d-carboxypeptidase, the tetrapeptide substrate was generated by hydrolysis of the C-terminald-Lac residue of the stem pentadepsipeptide in the periplasm in competition with the exchange reaction catalyzed byd,d-transpeptidases. InNonomuraeasp. strain ATCC 39727, the contribution ofl,d-transpeptidases to glycopeptide resistance was limited by the incomplete conversion of pentapeptides into tetrapeptides despite the production of a cytoplasmic metallo-d,d-carboxypeptidase. Since the level of drug production exceeds the level of resistance, we propose thatl,d-transpeptidases merely act as a tolerance mechanism in this bacterium.

scholarly journals Combination of Pantothenamides with Vanin Inhibitors as a Novel Antibiotic Strategy against Gram-Positive Bacteria

2013 ◽  
Vol 57 (10) ◽  
pp. 4794-4800 ◽  
Author(s):  
Patrick A. M. Jansen ◽  
Pedro H. H. Hermkens ◽  
Patrick L. J. M. Zeeuwen ◽  
Peter N. M. Botman ◽  
Richard H. Blaauw ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Acid Synthesis ◽  
Spectrometric Analysis ◽  
Gram Positive ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
New Compounds ◽  
Emergence Of Resistance ◽  
Hydrolysis Of

ABSTRACTThe emergence of resistance against current antibiotics calls for the development of new compounds to treat infectious diseases. Synthetic pantothenamides are pantothenate analogs that possess broad-spectrum antibacterial activityin vitroin minimal media. Pantothenamides were shown to be substrates of the bacterial coenzyme A (CoA) biosynthetic pathway, causing cellular CoA depletion and interference with fatty acid synthesis. In spite of their potential use and selectivity for bacterial metabolic routes, these compounds have never made it to the clinic. In the present study, we show that pantothenamides are not active as antibiotics in the presence of serum, and we found that they were hydrolyzed by ubiquitous pantetheinases of the vanin family. To address this further, we synthesized a series of pantetheinase inhibitors based on a pantothenate scaffold that inhibited serum pantetheinase activity in the nanomolar range. Mass spectrometric analysis showed that addition of these pantetheinase inhibitors prevented hydrolysis of pantothenamides by serum. We found that combinations of these novel pantetheinase inhibitors and prototypic pantothenamides like N5-Pan and N7-Pan exerted antimicrobial activityin vitro, particularly against Gram-positive bacteria (Staphylococcus aureus,Staphylococcus epidermidis,Streptococcus pneumoniae, andStreptococcus pyogenes) even in the presence of serum. These results indicate that pantothenamides, when protected against degradation by host pantetheinases, are potentially useful antimicrobial agents.

scholarly journals New Insight into the Ochratoxin A Biosynthetic Pathway through Deletion of a Nonribosomal Peptide Synthetase Gene in Aspergillus carbonarius

2012 ◽  
Vol 78 (23) ◽  
pp. 8208-8218 ◽  
Author(s):  
Antonia Gallo ◽  
Kenneth S. Bruno ◽  
Michele Solfrizzo ◽  
Giancarlo Perrone ◽  
Giuseppina Mulè ◽  
...  
Keyword(s):  
Ochratoxin A ◽  
Biosynthetic Pathway ◽  
Nonribosomal Peptide Synthetase ◽  
Gene Encoding ◽  
Nonribosomal Peptide ◽  
Content Type ◽  
Peptide Synthetase ◽  
Ochratoxin Α ◽  
Hydrolysis Of ◽  
Insight Into

ABSTRACTOchratoxin A (OTA), a mycotoxin produced byAspergillusandPenicilliumspecies, is composed of a dihydroisocoumarin ring linked to phenylalanine, and its biosynthetic pathway has not yet been completely elucidated. Most of the knowledge regarding the genetic and enzymatic aspects of OTA biosynthesis has been elucidated inPenicilliumspecies. InAspergillusspecies, onlypksgenes involved in the initial steps of the pathway have been partially characterized. In our study, the inactivation of a gene encoding a nonribosomal peptide synthetase (NRPS) in OTA-producingA. carbonariusITEM 5010 has eliminated the ability of this fungus to produce OTA. This is the first report on the involvement of annrpsgene product in OTA biosynthetic pathway in anAspergillusspecies. The absence of OTA and ochratoxin α, the isocoumaric derivative of OTA, and the concomitant increase of ochratoxin β, the dechloro analog of ochratoxin α, were observed in the liquid culture of transformed strain. The data provide the first evidence that the enzymatic step adding phenylalanine to polyketide dihydroisocoumarin precedes the chlorination step to form OTA inA. carbonariusand that ochratoxin α is a product of hydrolysis of OTA, giving an interesting new insight into the biosynthetic pathway of the toxin.

scholarly journals Peptidoglycan Cross-Linking Activity of L,D-Transpeptidases from Clostridium difficile and Inactivation of These Enzymes by β-Lactams

2017 ◽  
Vol 62 (1) ◽  
Author(s):  
Laetitia Sütterlin ◽  
Zainab Edoo ◽  
Jean-Emmanuel Hugonnet ◽  
Jean-Luc Mainardi ◽  
Michel Arthur
Keyword(s):  
Mass Spectrometry ◽  
Clostridium Difficile ◽  
Cross Linking ◽  
Content Type ◽  
Catalytic Activities ◽  
Cross Links ◽  
Covalent Adducts ◽  
The Stability ◽  
Hydrolysis Of ◽  
Insight Into

ABSTRACT In most bacteria, the essential targets of β-lactam antibiotics are the d , d -transpeptidases that catalyze the last step of peptidoglycan polymerization by forming 4→3 cross-links. The peptidoglycan of Clostridium difficile is unusual since it mainly contains 3→3 cross-links generated by l , d -transpeptidases. To gain insight into the characteristics of C. difficile peptidoglycan cross-linking enzymes, we purified the three putative C. difficile l , d -transpeptidase paralogues Ldt Cd1 , Ldt Cd2 , and Ldt Cd3 , which were previously identified by sequence analysis. The catalytic activities of the three proteins were assayed with a disaccharide-tetrapeptide purified from the C. difficile cell wall. Ldt Cd2 and Ldt Cd3 catalyzed the formation of 3→3 cross-links ( l , d -transpeptidase activity), the hydrolysis of the C-terminal d -Ala residue of the disaccharide-tetrapeptide substrate ( l , d -carboxypeptidase activity), and the exchange of the C-terminal d -Ala for d -Met. Ldt Cd1 displayed only l , d -carboxypeptidase activity. Mass spectrometry analyses indicated that Ldt Cd1 and Ldt Cd2 were acylated by β-lactams belonging to the carbapenem (imipenem, meropenem, and ertapenem), cephalosporin (ceftriaxone), and penicillin (ampicillin) classes. Acylation of Ldt Cd3 by these β-lactams was not detected. The acylation efficacy of Ldt Cd1 and Ldt Cd2 was higher for the carbapenems (480 to 6,600 M −1 s −1 ) than for ampicillin and ceftriaxone (3.9 to 82 M −1 s −1 ). In contrast, the efficacy of the hydrolysis of β-lactams by Ldt Cd1 and Ldt Cd2 was higher for ampicillin and ceftriaxone than for imipenem. These observations indicate that Ldt Cd1 and Ldt Cd2 are inactivated only by β-lactams of the carbapenem class due to a combination of rapid acylation and the stability of the resulting covalent adducts.

A review on the hypoglycemic properties of selected non-leafy vegetables in Malaysia

2019 ◽  
Vol 49 (6) ◽  
pp. 1113-1125 ◽  
Author(s):  
Seok-Tyug Tan ◽  
Seok-Shin Tan
Keyword(s):  
Type 2 Diabetes ◽  
Mechanism Of Action ◽  
Fruits And Vegetables ◽  
Underlying Mechanism ◽  
Leafy Vegetables ◽  
Health Concern ◽  
Content Type ◽  
Lady’S Finger ◽  
Frequent Consumption

Purpose Non-communicable diseases such as type 2 diabetes, hypertension, cancers and cardiovascular diseases have become a major health concern globally. As literature claims that frequent consumption of fruits and vegetables can delay the onset of type 2 diabetes and its complications, this paper aims to evaluate the potential hypoglycemic properties in five types of non-leafy vegetables (pumpkin, sweet potato, bitter gourd, onion and lady’s finger), which are commonly available in Malaysia. Design/methodology/approach Articles were identified through several main search engines, including Pubmed, Google Scholar, Taylor and Francis Online, EDS, Wiley, ScienceDirect and Scopus. The search was limited to selected keywords to refine the outcome. Findings All the five types of non-leafy vegetables demonstrate hypoglycemic properties to some extent. Emerging findings indicate that there are several phytonutrients in the non-leafy vegetables contributing to the hypoglycemic effects. To date, the underlying mechanism of action remains to be elucidated, although a number of potential mechanisms of action have been proposed in the literature. Originality/value This review provides some insights into the hypoglycemic properties in non-leafy vegetables. In addition, phytonutrients that are responsible for the hypoglycemic effects and their mechanism of action are also highlighted.

scholarly journals Metformin Ameliorates Lipopolysaccharide-Induced Depressive-Like Behaviors and Abnormal Glutamatergic Transmission

Biology ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 359
Author(s):  
Jiang Chen ◽  
Tian Zhou ◽  
A-Min Guo ◽  
Wen-Bing Chen ◽  
Dong Lin ◽  
...  
Keyword(s):  
Tail Suspension Test ◽  
Underlying Mechanism ◽  
Glutamatergic Transmission ◽  
Comorbid Depression ◽  
First Line ◽  
Antidepressant Effects ◽  
Swimming Test ◽  
Insight Into ◽  
Line Drug

Metformin, a first-line drug for type 2 diabetes mellitus (T2DM), has been found to reduce depressive symptoms in patients with comorbid depression and other diseases. However, it is largely unclear how metformin ameliorates depressive-like behaviors. Here, we used lipopolysaccharide (LPS) to induce depressive-like behaviors in mice and found that LPS-treated mice exhibited increased immobility in the forced swimming test (FST) and tail suspension test (TST), as well as increased glutamatergic transmission. Furthermore, metformin administration in the LPS-treated mice ameliorated depressive-like behaviors and elevated glutamatergic transmission. Our results suggest that metformin has antidepressant effects and can correct abnormal glutamatergic transmission, providing an insight into the underlying mechanism by which metformin acts against depression.

scholarly journals In-store interactive advertising screens: the effect of interactivity on impulse buying explained by self-agency

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Anne Moes ◽  
Marieke Fransen ◽  
Bob Fennis ◽  
Tibert Verhagen ◽  
Harry van Vliet
Keyword(s):  
Field Experiments ◽  
Underlying Mechanism ◽  
Impulse Buying ◽  
Content Type ◽  
Mediating Role ◽  
Interactive Advertising ◽  
Impulse Purchases ◽  
Mediating Factor ◽  
Insight Into

PurposePhysical stores are increasingly dependent on impulse visits and the impulse purchases of passers-by. Interactive advertising screens in store windows could help retailers increase impulse-visit urges and impulse-buying urges. However, the effects of interactive screens in physical surroundings have not been studied before. Therefore, this study aimed to examine the effect of interactive screens on impulse urges and gain insight into the underlying mechanism that explains the possible effect.Design/methodology/approachAn interactive screen was placed in a store window. Using three field experiments, we studied the effect of interactivity-level (high vs low) on the impulse-visit and impulse-buying urges of passers-by, and the mediating role of self-agency in these effects.FindingsHighly interactive (compared to less interactive) advertising screens in store windows positively affect impulse-visit and impulse-buying urges through self-agency. Retailers can therefore use interactive advertising screens to increase the number of impulse purchases if feelings of self-agency are activated.Originality/valueThis is the first study to examine the extent to which interactive screens in a store window enhance the impulse-visit and impulse-buying urges of passers-by and the mediating factor of these effects. By conducting three field experiments, we achieved a high external validity and managed to share very reliable results owing to the replication of the findings.

scholarly journals Hydrolysis of Clavulanate by Mycobacterium tuberculosis β-Lactamase BlaC Harboring a Canonical SDN Motif

2015 ◽  
Vol 59 (9) ◽  
pp. 5714-5720 ◽  
Author(s):  
Daria Soroka ◽  
Inès Li de la Sierra-Gallay ◽  
Vincent Dubée ◽  
Sébastien Triboulet ◽  
Herman van Tilbeurgh ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Fold Increase ◽  
Mycobacterium Abscessus ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Content Type ◽  
Emergence Of Resistance ◽  
Hydrolysis Of ◽  
Sequential Formation

ABSTRACTCombinations of β-lactams with clavulanate are currently being investigated for tuberculosis treatment. SinceMycobacterium tuberculosisproduces a broad spectrum β-lactamase, BlaC, the success of this approach could be compromised by the emergence of clavulanate-resistant variants, as observed for inhibitor-resistant TEM variants in enterobacteria. Previous analyses based on site-directed mutagenesis of BlaC have led to the conclusion that this risk was limited. Here, we used a different approach based on determination of the crystal structure of β-lactamase BlaMAbofMycobacterium abscessus, which efficiently hydrolyzes clavulanate. Comparison of BlaMAband BlaC allowed for structure-assisted site-directed mutagenesis of BlaC and identification of the G132N substitution that was sufficient to switch the interaction of BlaC with clavulanate from irreversible inactivation to efficient hydrolysis. The substitution, which restored the canonical SDN motif (SDG→SDN), allowed for efficient hydrolysis of clavulanate, with a more than 104-fold increase inkcat(0.41 s−1), without affecting the hydrolysis of other β-lactams. Mass spectrometry revealed that acylation of BlaC and of its G132N variant by clavulanate follows similar paths, involving sequential formation of two acylenzymes. Decarboxylation of the first acylenzyme results in a stable secondary acylenzyme in BlaC, whereas hydrolysis occurs in the G132N variant. The SDN/SDG polymorphism defines two mycobacterial lineages comprising rapidly and slowly growing species, respectively. Together, these results suggest that the efficacy of β-lactam–clavulanate combinations may be limited by the emergence of resistance. β-Lactams active without clavulanate, such as faropenem, should be prioritized for the development of new therapies.

scholarly journals Hyperglycemic Emergencies Associated With Covid-19 Vaccination: A Case Series And Discussion

2021 ◽  
Author(s):  
Hanna J Lee ◽  
Alen Sajan ◽  
Yaron Tomer
Keyword(s):  
Case Series ◽  
Underlying Mechanism ◽  
Early Evaluation ◽  
Bidirectional Relationship ◽  
History Of ◽  
Hyperosmolar Hyperglycemic Syndrome ◽  
Insight Into ◽  
New Onset Diabetes Mellitus ◽  
Hba1c Levels

Abstract Context Hyperglycemic emergencies such as diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic syndrome (HHS) and new-onset diabetes mellitus (DM) have been reported in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Hyperglycemia is a predictor of poor prognosis in COVID-19 disease. Objectives The objective of this work is to describe a case series of HHS and/or DKA likely triggered by the COVID-19 vaccine. The aim is to alert physicians of the potential hyperglycemic complications from the COVID-19 vaccination and to provide further insight into the underlying mechanism of the bidirectional relationship between SARS-CoV-2 and DM. Case description All 3 patients developed HHS and/or DKA within 2-10 days of the COVID-19 vaccination. PCR testing for SARS-CoV-2 was negative and other clinical precipitating factors were excluded. Two patients had a history of type 2 DM (T2DM) with pre-admission HbA1c levels of 7.0-7.5% while one patient was newly diagnosed with T2DM during the hospitalization. They were each treated with insulin infusion and were discharged on subcutaneous insulin therapy. Due to the rapid resolution of the hyperglycemia, insulin was discontinued in all patients within 8 weeks and they remain well-controlled on oral DM medications. Conclusion Severe hyperglycemia including HHS and DKA may be triggered by COVID-19 vaccination. Early evaluation and screening of patients with hyperglycemic symptoms after COVID-19 vaccination is recommended. The vaccine-induced hyperglycemia may provide further insight into the underlying pathogenesis caused by the SARS-CoV-2 infection itself. The underlying robust inflammatory response and “cytokine storm” may be the primary precipitant.

scholarly journals Insights into the catalytic properties of the mitochondrial rhomboid protease PARL

2020 ◽  
Author(s):  
Laine Lysyk ◽  
Raelynn Brassard ◽  
Elena Arutyunova ◽  
Verena Siebert ◽  
Zhenze Jiang ◽  
...  
Keyword(s):  
Catalytic Properties ◽  
Side Chain ◽  
Turnover Rates ◽  
Rhomboid Protease ◽  
Mitochondrial Homeostasis ◽  
Substrate Preferences ◽  
Rhomboid Proteases ◽  
Hydrolysis Of ◽  
Insight Into

AbstractThe rhomboid protease PARL is a critical regulator of mitochondrial homeostasis through its cleavage of substrates such as PINK1, PGAM5, and Smac, which have crucial roles in mitochondrial quality control and apoptosis. To gain insight into the catalytic properties of the PARL protease, we expressed human PARL in yeast and used FRET-based kinetic assays to measure proteolytic activity in vitro. We show PARL activity in detergent is enhanced by cardiolipin. Significantly higher turnover rates are observed for PARL reconstituted in proteoliposomes, with Smac being cleaved most rapidly at a rate of 1 min−1. PGAM5 is cleaved with the highest efficiency compared to PINK1 and Smac. In proteoliposomes, a truncated β-cleavage form of PARL is more active than the full-length enzyme for hydrolysis of PINK1, PGAM5 and Smac. Multiplex substrate profiling reveals a substrate preference for PARL with a bulky side chain Phe in P1, which is distinct from small side chain residues typically found with bacterial rhomboid proteases. This study using recombinant PARL provides fundamental insights into its catalytic activity and substrate preferences.

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