ATP-dependent D-alanine:D-alanine ligase (Ddl) is a part of biochemical machinery involved in peptidoglycan biosynthesis, as it catalyzes the formation of the terminal D-ala-D-ala dipeptide of the ...peptidoglycan precursor UDPMurNAc-pentapeptide. Inhibition of Ddl prevents bacterial growth, which makes this enzyme an attractive and viable target in the urgent search of novel effective antimicrobial drugs. To address the problem of a relentless increase in resistance to known antimicrobial agents we focused our attention to discovery of novel ATP-competitive inhibitors of Ddl.
Encouraged by recent successful attempts to find selective ATP-competitive inhibitors of bacterial enzymes we designed, synthesized and evaluated a library of 6-arylpyrido2,3-dpyrimidine-based compounds as inhibitors of Escherichia coli DdlB. Inhibitor binding to the target enzyme was subsequently confirmed by surface plasmon resonance and studied with isothermal titration calorimetry. Since kinetic analysis indicated that 6-arylpyrido2,3-dpyrimidines compete with the enzyme substrate ATP, inhibitor binding to the ATP-binding site was additionally studied with docking. Some of these inhibitors were found to possess antibacterial activity against membrane-compromised and efflux pump-deficient strains of E. coli.
We discovered new ATP-competitive inhibitors of DdlB, which may serve as a starting point for development of more potent inhibitors of DdlB that could include both, an ATP-competitive and D-Ala competitive moiety.
The d-aspartate ligase of Enterococcus faecium (Aslfm) is an attractive target for the development of narrow-spectrum antibacterial agents that are active against multidrug-resistant E. faecium. ...Although there is currently little available information regarding the structural characteristics of Aslfm, we exploited the knowledge that this enzyme belongs to the ATP-grasp superfamily to target its ATP binding site. In the first design stage, we synthesized and screened a small library of known ATP-competitive inhibitors of ATP-grasp enzymes. A series of amino-oxazoles derived from bacterial biotin carboxylase inhibitors showed low micromolar activity. The most potent inhibitor compound 12, inhibits Aslfm with a Ki value of 2.9 μM. In the second design stage, a validated ligand-based pharmacophore modeling approach was used, taking the newly available inhibition data of an initial series of compounds into account. Experimental evaluation of the virtual screening hits identified two novel structural types of Aslfm inhibitors with 7-amino-9H-purine (18) and 7-amino-1H-pyrazolo3,4-dpyrimidine (30 and 34) scaffolds, and also with Ki values in the low micromolar range. Investigation the inhibitors modes of action confirmed that these compounds are competitive with respect to the ATP molecule. The binding of inhibitors to the target enzyme was also studied using isothermal titration calorimetry (ITC). Compounds 6, 12, 18, 30 and 34 represent the first inhibitors of Aslfm reported to date, and are an important step forward in combating infections due to E. faecium.
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•Synthesized amino-oxazoles identified as Aslfm inhibitors.•Construction of ligand-based pharmacophores and virtual screening experiments.•7-Amino-purines and 7-amino-pyrazolopyrimidines identified as Aslfm inhibitors.•Kinetic and isothermal titration calorimetry measurements.
The critical micelle concentration, cmc, and the degree of micelle ionization, β, of decyltrimethylammonium chloride (DeTAC), dodecyltrimethylammonium chloride (DTAC) and tetradecyltrimethylammonium ...chloride (TTAC) in water, 0.01 M, and 0.1 M NaCl solution were determined from the electrical conductivity data in the temperature range from 278.15 to 328.15 K. It has been found that cmc is decreasing with increasing surfactant chain length and increasing concentration of added NaCl, whereas the temperature dependence of cmc shows the typical U-shaped form with a minimum around (306 ± 3) K. Further, β is decreasing with lengthening the alkyl chain of surfactant and increasing with increasing temperature, but no distinct influence of added salt has been found actually. It can be concluded that the effect of electrolyte on micelle ionization is quite complex.
Airborne particulate matter (PM) is a vector of many toxic pollutants, including polyaromatic hydrocarbons (PAHs) and their derivatives. Especially harmful is the fine fraction (PM
), which ...penetrates deep into the lungs during inhalation and causes various diseases. Amongst PM
components with toxic potential are nitrated PAHs (NPAHs), knowledge of which is still rudimentary. Three of the measured NPAHs (1-nitropyrene (1-nP), 9-nitroanthracene (9-nA), and 6-nitrochrysene (6-nC)) were detected in ambient PM
from Ljubljana, Slovenia, along with thirteen non-nitrated PAHs. The highest concentrations of pollutants, which are closely linked with incomplete combustion, were observed in the cold part of the year, whereas the concentrations of NPAHs were roughly an order of magnitude lower than those of PAHs throughout the year. Further on, we have evaluated the toxicity of four NPAHs, including 6-nitrobenzoapyrene (6-nBaP), to the human kidney cell line, HEK293T. The most potent was 1-nP (IC
= 28.7 µM), followed by the other three NPAHs, whose IC
was above 400 or 800 µM. According to our cytotoxicity assessment, atmospheric 1-nP is the most harmful NPAH among the investigated ones. Despite low airborne concentrations of NPAHs in ambient air, they are generally considered harmful to human health. Therefore, systematic toxicological assessment of NPAHs at different trophic levels, starting with cytotoxicity testing, is necessary in order to accurately evaluate their threat and adopt appropriate abatement strategies.
Airborne particulate matter (PM) is a vector of many toxic pollutants, including polyaromatic hydrocarbons (PAHs) and their derivatives. Especially harmful is the fine fraction (PMsub.2.5), which ...penetrates deep into the lungs during inhalation and causes various diseases. Amongst PMsub.2.5 components with toxic potential are nitrated PAHs (NPAHs), knowledge of which is still rudimentary. Three of the measured NPAHs (1-nitropyrene (1-nP), 9-nitroanthracene (9-nA), and 6-nitrochrysene (6-nC)) were detected in ambient PMsub.2.5 from Ljubljana, Slovenia, along with thirteen non-nitrated PAHs. The highest concentrations of pollutants, which are closely linked with incomplete combustion, were observed in the cold part of the year, whereas the concentrations of NPAHs were roughly an order of magnitude lower than those of PAHs throughout the year. Further on, we have evaluated the toxicity of four NPAHs, including 6-nitrobenzoapyrene (6-nBaP), to the human kidney cell line, HEK293T. The most potent was 1-nP (ICsub.50 = 28.7 µM), followed by the other three NPAHs, whose ICsub.50 was above 400 or 800 µM. According to our cytotoxicity assessment, atmospheric 1-nP is the most harmful NPAH among the investigated ones. Despite low airborne concentrations of NPAHs in ambient air, they are generally considered harmful to human health. Therefore, systematic toxicological assessment of NPAHs at different trophic levels, starting with cytotoxicity testing, is necessary in order to accurately evaluate their threat and adopt appropriate abatement strategies.
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