New library of pyrazole-imidazo[1,2-α]pyridine molecular conjugates: Synthesis, antibacterial activity and molecular docking studies.

A library of novel pyrazole-imidazo[1,2-α]pyridine scaffolds was designed and synthesized through a one-pot three-component tandem reaction. The structures of synthesized conjugates were confirmed by spectroscopic techniques (NMR, IR and HRMS). In vitro antibacterial evaluation of the twelve synthesized molecules (7a, 8a-k) against methicillin-resistant Staphylococcus aureus and normal strains of Escherichia coli, Salmonella typhimurium, Klebsiella pneumonia and Pseudomonas aeruginosa established 8b, 8d, 8e, 8h and 8i as potent antibacterial agents with superior minimum bactericidal concentration, compared with standard drug ciprofloxacin. Molecular docking studies of all active compounds into the binding site of glucosamine-6-phosphate synthase were further performed in order to have a comprehensive understanding of putative binding modes within the active sites of the receptor.

Virtual Screening of Novel Glucosamine-6-Phosphate Synthase Inhibitors.

BACKGROUND: Infections caused by microorganisms are the major cause of death today. The tremendous and improper use of antimicrobial agents leads to antimicrobial resistance. AIM AND OBJECTIVE: Various currently available antimicrobial drugs are inadequate to control the infections and lead to various adverse drug reactions. Efforts based on computer-aided drug design (CADD) can excavate a large number of databases to generate new, potent hits and minimize the requirement of time as well as money for the discovery of newer antimicrobials. Pharmaceutical sciences also have made development with advances in drug designing concepts. The current research article focuses on the study of various G-6-P synthase inhibitors from literature cited molecular database. Docking analysis was conducted and ADMET data of various molecules was evaluated by Schrodinger Glide and PreADMET software, respectively. Here, the results presented efficacy of various inhibitors towards enzyme G-6-P synthase. Docking scores, binding energy and ADMET data of various molecules showed good inhibitory potential toward G-6-P synthase as compared to standard antibiotics. This novel antimicrobial drug target G-6-P synthase has not so extensively been explored for its application in antimicrobial therapy, so the work done so far proved highly essential. This article has helped the drug researchers and scientists to intensively explore about this wonderful antimicrobial drug target. MATERIALS AND METHODS: The Schrodinger, Inc. (New York, USA) software was utilized to carry out the computational calculations and docking studies. The hardware configuration was Intel® core (TM) i5-4210U CPU @ 2.40GHz, RAM memory 4.0 GB under 64-bit window operating system. The ADMET data was calculated by using the PreADMET tool (PreADMET ver. 2.0). All the computational work was completed in the Laboratory for Enzyme Inhibition Studies, Department of Pharmaceutical Sciences, M.D. University, Rohtak, INDIA. RESULTS: Molecular docking studies were carried out to identify the binding affinities and interaction between the inhibitors and the target proteins (G-6-P synthase) by using Glide software (Schrodinger Inc. U.S.A.-Maestro version 10.2). Grid-based Ligand Docking with Energetic (Glide) is one of the most accurate docking softwares available for ligand-protein, protein-protein binding studies. A library of hundreds of available ligands was docked against targeted proteins G-6-P synthase having PDB ID 1moq. Results of docking are shown in Table 1 and Table 2. Results of G-6-P synthase docking showed that some compounds were found to have comparable docking score and binding energy (kj/mol) as compared to standard antibiotics. Many of the ligands showed hydrogen bond interaction, hydrophobic interactions, electrostatic interactions, ionic interactions and π- π stacking with the various amino acid residues in the binding pockets of G-6-P synthase. CONCLUSION: The docking study estimated free energy of binding, binding pose andglide score and all these parameters provide a promising tool for the discovery of new potent natural inhibitors of G-6-P synthase. These G-6-P synthase inhibitors could further be used as antimicrobials. Here, a detailed binding analysis and new insights of inhibitors from various classes of molecules were docked in binding cavity of G-6-P synthase. ADME and toxicity prediction of these compounds will further accentuate us to study these compounds in vivo. This information will possibly present further expansion of effective antimicrobials against several microbial infections.

Removal of O-GlcNAcylation is important for pig preimplantation development.

Glucose has been recognized as an energy source for a long time, but it has recently been suggested that the hexosamine biosynthesis pathway (HBP) and downstream protein O-GlcNAcylation have important functions in mouse preimplantation development. Thus, whether or not O-GlcNAcylation was present and what functions O-GlcNAcylation has in pig preimplantation development were investigated in the present study. The expressions of mRNA of glutaminefructose-6-phosphate aminotransferase (Gfpt), O-GlcNAc transferase (Ogt) and O-GlcNAcase (Oga), which are involved in the HBP and O-GlcNAc cycling, were examined in pig parthenogenetic diploids at each preimplantation developmental stage. Gfpt and Ogt were detected in diploids at all stages. Though Oga was detected at all stages except the 4-cell stage, OGA proteins were detected in diploids from the 2-cell to blastocyst stage. Furthermore, O-GlcNAcylated proteins in MII oocytes and diploids were also detected by immunofluorescence at every stage. Inhibition of OGT by 4.0 mM BADGP did not affect development up to the blastocyst stage, while inhibition of OGA by 300 µM PUGNAc decreased the proportion of diploids beyond the 4-cell stage. Four-cell diploids cultured with PUGNAc until 48 h developed to the blastocyst stage after culture in a PUGNAc-free medium until 144 h after electrostimulation. RNA polymerase II (Pol II) phosphorylation, which indicates the onset of mRNA transcription, was detected in nuclei of diploids in the control group at 48 h but not in the PUGNAc-treated group. These results indicate that HBP and O-GlcNAcylation have important functions in pig preimplantation development and that inhibition of OGA is fatal for development. It is also suggested that OGA inhibition disrupts normal Pol II regulation and may cause a zygotic gene activation error.

Anticandidal properties of N-acylpeptides containing an inhibitor of glucosamine-6-phosphate synthase.

A series of N-acyl peptides 1-9, containing an inhibitor of glucosamine-6-phosphate synthase have been synthesised and tested against Candida strains. N-Acylated peptides inhibit glucosamine-6-phosphate synthase in cell free extracts from Candida albicans. Antifungal activities of the tested compounds correlated with their lipophilic properties. Peptides acylated with decanoic acid were found to be the most potent in the series. N-decanoylpeptides also showed activity against Candida albicans Gu5 resistant mutant with Cdr1 and Cdr2 drug extrusion proteins that causes MDR by an active efflux mechanism.

Functional regulation of glutamine:fructose-6-phosphate aminotransferase 1 (GFAT1) of Drosophila melanogaster in a UDP-N-acetylglucosamine and cAMP-dependent manner.

Glutamine:fructose-6-phosphate aminotransferase (GFAT; EC 2.6.1.16) expression is tightly regulated in the context of amino sugar synthesis in many organisms from yeast to humans by transcriptional and post-translational processes. We have cloned the cDNA of the GFAT1 of Drosophila melanogaster (Dmel/Gfat1). One of the two putative protein kinase A (PKA) phosphorylation sites proposed for the regulation of human GFAT1 [Zhou, Huynh, Hoffmann, Crook, Daniels, Gulve and McClain (1998) Diabetes 47, 1836-1840] is conserved in Dmel/GFAT1. In the other one the reactive serine has been converted to a cysteine, making further access by PKA unlikely. The Dmel/Gfat1 gene is localized at position 81F on the right arm of chromosome 3. By whole-mount in situ hybridization specific expression of Dmel/GFAT1 was detected in embryonic chitin-synthesizing tissues and in the corpus cells of salivary glands from late third larval instar. Expressing Dmel/GFAT1 in yeast we showed that Dmel/GFAT1 activity is controlled by UDP-N-acetylglucosamine and PKA in the yeast total protein extract system. We propose a model for the independent regulation of the Dmel/GFAT1 enzyme by feedback inhibition and PKA.

Extremophilic orgainisms as and unexplored source fo antifungal compounds.

Extracts of the biomasses and fermentation broths of 217 extremophilic microorganisms isolated from a number of locales were screened for antifungal activity using whole-cell and mechanism-based in vitro assays. Importantly, eleven broth extracts had activity against several Candida species and Aspergillus fumigatus in whole-cell in vitro assays. One broth specifically inhibited (1,3)beta-glucan synthase activity and four specifically inhibited ketol-isomerase activity, suggesting a mode of action of the antifungal compound(s) present in these extracts. The extract from one thermophile, a novel species of Pseudomonas, was fractionated, an active compound purified and its structure determined. The compound was identified as pyochelin, a previously identified iron-binding compound with heretofore undescribed antifungal activity. To our knowledge, this is the first report demonstrating that extremophiles synthesize compounds that have antifungal activity.

Cytotoxic mechanisms of glutamine antagonists in mouse L1210 leukemia.

The glutamine antagonists, acivicin (NSC 163501), azaserine (NSC 742), and 6-diazo-5-oxo-L-norleucine (DON) (NSC 7365), are potent inhibitors of many glutamine-dependent amidotransferases in vitro. Experiments performed with mouse L1210 leukemia growing in culture show that each antagonist has different sites of inhibition in nucleotide biosynthesis. Acivicin is a potent inhibitor of CTP and GMP synthetases and partially inhibits N-formylglycineamidine ribotide (FGAM) synthetase of purine biosynthesis. DON inhibits FGAM synthetase, CTP synthetase, and glucosamine-6-phosphate isomerase. Azaserine inhibits FGAM synthetase and glucosamine-6-phosphate isomerase. Large accumulations of FGAR and its di- and triphosphate derivatives were observed for all three antagonists which could interfere with the biosynthesis of nucleic acids, providing another mechanism of cytotoxicity. Acivicin, azaserine, and DON are not potent inhibitors of carbamyl phosphate synthetase II (glutamine-hydrolyzing) and amidophosphoribosyltransferase in leukemia cells growing in culture although there are reports of such inhibitions in vitro. Blockade of de novo purine biosynthesis by these three antagonists results in a "complementary stimulation" of de novo pyrimidine biosynthesis.

Effect of anti-inflammatory agent on L-glutamine-D-fructose-6-phosphate transaminase.

The enzyme L-glutamineD-fructose-6-phosphate aminotransferase (EC 2.6.1.16) was isolated, partially characterized, and purified from the gastric mucosa of dogs. A new method, using 14C-fructose-6-phosphate, has been developed for the estimation of the enzyme activity. Several classes of standard anti-inflammatory agents including acetyl-salicylic acid, salicylic acid, flufenamic acid, phenyl-butazone, indometacin, mefenamic acid, oxyphenyl-butazone, antipyrine, aminophenazone, allopurinol, cortisol, and dimethylsulfoxide (DMSO) were found to be inhibitors of this enzyme. The property of inhibition of this amino-transferase could, thus, be used as a rapid in vitro test method for the primary screening of potential anti-inflammatory agents.