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Biochemistry Oct 2019NeuB is a bacterial sialic acid synthase used by neuroinvasive bacteria to synthesize -acetylneuraminate (NeuNAc), helping them to evade the host immune system. NeuNAc...
NeuB is a bacterial sialic acid synthase used by neuroinvasive bacteria to synthesize -acetylneuraminate (NeuNAc), helping them to evade the host immune system. NeuNAc oxime is a potent slow-binding NeuB inhibitor. It dissociated too slowly to be detected experimentally, with initial estimates of its residence time in the active site being >47 days. This is longer than the lifetime of a typical bacterial cell, meaning that inhibition is effectively irreversible. Inhibition data fitted well to a model that included a pre-equilibration step with a of 36 μM, followed by effectively irreversible conversion to an E*·I complex, with a of 5.6 × 10 s. Thus, the inhibitor can subvert ligand release and achieve extraordinary residence times in spite of a relatively modest initial dissociation constant. The crystal structure showed the oxime functional group occupying the phosphate-binding site normally occupied by the substrate PEP and the tetrahedral intermediate. There was an ≈10% residual rate at high inhibitor concentrations regardless of how long NeuB and NeuNAc oxime were preincubated together. However, complete inhibition was achieved by incubating NeuNAc oxime with the actively catalyzing enzyme. This requirement for the enzyme to be actively turning over for the inhibitor to bind to the second subunit demonstrated an important role for intersubunit communication in the inhibitory mechanism.
Topics: 3-Deoxy-7-Phosphoheptulonate Synthase; Aldehyde-Lyases; Catalytic Domain; Crystallization; Crystallography, X-Ray; Genetic Vectors; Kinetics; N-Acetylneuraminic Acid; Neisseria meningitidis; Oximes; Oxo-Acid-Lyases; Protein Binding; Time Factors; Triose-Phosphate Isomerase
PubMed: 31549502
DOI: 10.1021/acs.biochem.9b00654 -
Bioorganic & Medicinal Chemistry Letters Apr 2022In order to application of cholesterol as pesticidal agents, a series of oxime esters of cholesterol containing piperic acid-like fragments were semi-synthesized by...
Construction of new oxime esters of cholesterol containing piperic acid-like fragments as insecticidal agents against Aphis citricola Van der Goot (Homoptera: Aphididae) and Plutella xylostella Linnaeus (Lepidoptera: Plutellidae).
In order to application of cholesterol as pesticidal agents, a series of oxime esters of cholesterol containing piperic acid-like fragments were semi-synthesized by modification of cholesterol at the C-3 and C-6 positions. Their structures were characterized by H NMR, HRMS and mp, and their purity was determined by HPLC. Against Aphis citricola Van der Goot, derivatives Ib (R = 4-FPh) and In (R = 3,4-ethylenedioxystyryl) exhibited 5.0 and 4.8 folds more pronounced aphicidal activity of their precursor cholesterol. Against Plutella xylostella Linnaeus, compounds Ia (R = Ph) and If (R = 3,4-methylenedioxyphenyl) showed 2.2 and 2.0 folds more potent insecticidal activity of cholesterol. Their SARs were also observed.
Topics: Animals; Aphids; Cholesterol; Esters; Fatty Acids, Unsaturated; Insecticides; Lepidoptera; Molecular Structure; Moths; Oximes; Structure-Activity Relationship
PubMed: 35202810
DOI: 10.1016/j.bmcl.2022.128634 -
Chemical Research in Toxicology Mar 2021Oxime cholinesterase reactivators (oximes) are used to counteract organophosphate intoxication. Charged oximes are administered via intramuscular or intravenous...
Oxime cholinesterase reactivators (oximes) are used to counteract organophosphate intoxication. Charged oximes are administered via intramuscular or intravenous injection when the majority of dose is unmetabolized and is excreted as urine. In this study, the effects of selected double charged oximes were determined in the HK-2 cell line as a model for renal toxicity screening. Some effects on dehydrogenase activity were found for obidoxime, asoxime (syn. HI-6), K027, and K203. The effects of K868 and K869 were found to be unreliable due to rapid degradation of both chlorinated oximes in the assay medium, resulting for K868 in an isoxazole-pyridinium product.
Topics: Cell Line; Cholinesterase Reactivators; Dose-Response Relationship, Drug; Humans; Kidney; Molecular Structure; Oximes
PubMed: 33566584
DOI: 10.1021/acs.chemrestox.0c00489 -
Chemico-biological Interactions Jan 2019Despite its efficacy as a skin decontaminant of reactive organophosphates (OP), Dekon 139-a potassium salt of 2,3-butanedione monooxime (DAM)-is associated with adverse...
Despite its efficacy as a skin decontaminant of reactive organophosphates (OP), Dekon 139-a potassium salt of 2,3-butanedione monooxime (DAM)-is associated with adverse events related to percutaneous absorption largely due to its small size and lipophilicity. In order to address this physicochemical issue, we synthesized and evaluated the activity of a focused library of 14 hydrophilic oxime compounds, each designed with either a DAM or monoisonitrosoacetone (MINA) oxime tethered to a polar or charged scaffold in order to optimize the size, hydrophilicity, and oxime acidity. High-throughput colorimetric assays were performed with paraoxon (POX) as a model OP to determine the kinetics of POX inactivation by these compounds under various pH and temperature conditions. This primary screening led to the identification of 6 lead compounds, predominantly in the MINA series, which displayed superb catalytic activity by reducing the POX half-life (t) by 2-3 fold relative to Dekon 139. Our mechanistic studies show that POX inactivation by the oxime compounds occurred faster at a higher temperature and in a pH-dependent manner in which the negatively charged oximate species is ≥ 10-fold more effective than the neutral oxime species. Lastly, using one of the lead compounds, we demonstrated its promising efficacy for POX decontamination in porcine skin ex vivo, and showed its potent ability to protect acetylcholine esterase (AChE) through POX inactivation. In summary, we report the rational design and chemical biological validation of novel hydrophilic oximes which address an unmet need in therapeutic OP decontamination.
Topics: Acetylcholinesterase; Animals; Biocatalysis; Cholinesterase Inhibitors; Cholinesterase Reactivators; Dose-Response Relationship, Drug; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Kinetics; Molecular Structure; Oximes; Paraoxon; Skin; Structure-Activity Relationship; Swine; Temperature
PubMed: 30393113
DOI: 10.1016/j.cbi.2018.10.022 -
Toxicology and Applied Pharmacology Mar 2021The brain is a critical target for the toxic action of organophosphorus (OP) inhibitors of acetylcholinesterase (AChE) such as the nerve agent sarin. However, the... (Comparative Study)
Comparative Study
The tertiary oxime monoisonitrosoacetone penetrates the brain, reactivates inhibited acetylcholinesterase, and reduces mortality and morbidity following lethal sarin intoxication in guinea pigs.
The brain is a critical target for the toxic action of organophosphorus (OP) inhibitors of acetylcholinesterase (AChE) such as the nerve agent sarin. However, the available oxime antidote 2-PAM only reactivates OP-inhibited AChE in peripheral tissues. Monoisonitrosoacetone (MINA), a tertiary oxime, reportedly reactivates AChE in the central nervous system (CNS). The current study investigated whether MINA would be beneficial as a supplemental oxime treatment in preventing lethality and reducing morbidity following lethal sarin exposure, MINA supplement would improve AChE recovery in the body, and MINA would be detectable in the CNS. Guinea pigs were exposed to sarin and treated with atropine sulfate and 2-PAM at one minute. Additional 2-PAM or MINA was administered at 3, 5, 15, or 30 min after sarin exposure. Survival and morbidity were assessed at 2 and 24 h. AChE activity in brain and peripheral tissues was evaluated one hour after MINA and 2-PAM treatment. An in vivo microdialysis technique was used to determine partitioning of MINA into the brain. A liquid chromatography-tandem mass spectrometry method was developed for the analysis of MINA in microdialysates. MINA-treated animals exhibited significantly higher survival and lower morbidity compared to 2-PAM-treated animals. 2-PAM was significantly more effective in reactivating AChE in peripheral tissues, but only MINA reactivated AChE in the CNS. MINA was found in guinea pig brain microdialysate samples beginning at ~10 min after administration in a dose-related manner. The data strongly suggest that a centrally penetrating oxime could provide significant benefit as an adjunct to atropine and 2-PAM therapy for OP intoxication.
Topics: Acetylcholinesterase; Animals; Antidotes; Brain; Cholinesterase Reactivators; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Activation; Guinea Pigs; Male; Microdialysis; Organophosphate Poisoning; Oximes; Permeability; Pralidoxime Compounds; Sarin; Tissue Distribution
PubMed: 33548273
DOI: 10.1016/j.taap.2021.115443 -
Physiological Research 2011Current treatment of organophosphorus poisoning, resulting in overstimulation and desensitization of muscarinic and nicotinic receptors by acetylcholine (ACh), consists... (Comparative Study)
Comparative Study
Current treatment of organophosphorus poisoning, resulting in overstimulation and desensitization of muscarinic and nicotinic receptors by acetylcholine (ACh), consists of the administration of atropine and oxime reactivators. However, no versatile oxime reactivator has been developed yet and some mortality still remains after application of standard atropine treatment, probably due to its lack of antinicotinic action. In our study, we focused on the interesting non-acetylcholinesterase property of oximes, i.e. antinicotinic effect of reactivators. Two standard reactivators (HI-6, obidoxime) and two new compounds (K027 and K203) were chosen for in vitro (patch clamp) and in vivo (nerve-evoked muscle contraction) testings. Both examinations showed antinicotinic effects of the reactivators. In vitro inhibition of acetylcholine-evoked currents by obidoxime, HI-6 and K203 was equivalent while K027 was less potent. Similar order of potency was observed by the in vivo examinations. We thus confirm previous in vitro results, which describe antinicotinic effects of oxime reactivators, and furthermore, we show in vivo antagonism of oxime reactivators exerted by the inhibition of ACh effect on the nicotinic receptor in the neuromuscular junction. Taking together, the effects of tested oxime reactivators indicate an antagonism on both embryonic and adult form of the muscle nicotinic receptors.
Topics: Animals; Cholinesterase Reactivators; Dose-Response Relationship, Drug; Male; Nicotinic Antagonists; Obidoxime Chloride; Oximes; Pyridinium Compounds; Rats; Rats, Sprague-Dawley; Receptors, Nicotinic
PubMed: 21574759
DOI: 10.33549/physiolres.932105 -
European Journal of Medicinal Chemistry Mar 2015This paper reports the synthesis and cardiac activity of new β-blockers derived from (Z/E)-indeno[1,2-c]pyrazol-4(1H)-one oximes (5a,b). The latter compounds were...
This paper reports the synthesis and cardiac activity of new β-blockers derived from (Z/E)-indeno[1,2-c]pyrazol-4(1H)-one oximes (5a,b). The latter compounds were allowed to react with epichlorohydrin, followed by reacting the oxiranyl derivatives formed (6a,b) with some aliphatic amines to give the target compounds (Z/E)-1-phenyl-1H-indeno[1,2-c]pyrazol-4-one O-((2-hydroxy-3-(substituted amino)propyl)oxime (7a-c) and (Z/E)-1-methyl-1H-indeno[1,2-c]pyrazol-4-one O-((2-hydroxy-3-(substituted amino)propyl)oxime (8a-c). These final products 7a-c and 8a-c were evaluated for their ability to modulate the cardiac performance of a prototype mammalian heart. The results showed that, out of these molecules tested, 7b elicits a more potent depressant effect on contractility and relaxation, and competitively antagonizes β1-adrenergic receptors.
Topics: Adrenergic beta-1 Receptor Antagonists; Animals; Dose-Response Relationship, Drug; Esters; Male; Molecular Structure; Oximes; Pyrazoles; Rats; Rats, Wistar; Receptors, Adrenergic, beta-1; Structure-Activity Relationship
PubMed: 25618014
DOI: 10.1016/j.ejmech.2015.01.037 -
Organic Letters May 2018Mild conditions for oxime ligations via in situ generation of α-imino amide intermediates are reported. The evaluation of a variety of N-terminal N-phenylglycine...
Mild conditions for oxime ligations via in situ generation of α-imino amide intermediates are reported. The evaluation of a variety of N-terminal N-phenylglycine residues revealed that a metal-free, chemoselective oxidation was possible using oxygen as the only oxidant in buffer at pH 7.0. Moreover, selective unmasking of an inert residue by addition of potassium ferricyanide is demonstrated. These simple and mild conditions, which can be fine-tuned by the electronic properties of the N-phenylglycine residue, offer unique advantages over conventional approaches for oxime ligations.
Topics: Molecular Structure; Oxidation-Reduction; Oximes; Peptides
PubMed: 29694052
DOI: 10.1021/acs.orglett.8b00713 -
The Journal of Biological Chemistry Aug 2011The cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase, are primary targets of organophosphates (OPs). Exposure to OPs can lead to serious...
The cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase, are primary targets of organophosphates (OPs). Exposure to OPs can lead to serious cardiovascular complications, respiratory compromise, and death. Current therapy to combat OP poisoning involves an oxime reactivator (2-PAM, obidoxime, TMB4, or HI-6) combined with atropine and on occasion an anticonvulsant. Butyrylcholinesterase, administered in the plasma compartment as a bio-scavenger, has also shown efficacy but is limited by its strict stoichiometric scavenging, slow reactivation, and a propensity for aging. Here, we characterize 10 human (h) AChE mutants that, when coupled with an oxime, give rise to catalytic reactivation and aging resistance of the soman conjugate. With the most efficient human AChE mutant Y337A/F338A, we show enhanced reactivation rates for several OP-hAChE conjugates compared with wild-type hAChE when reactivated with HI-6 (1-(2'-hydroxyiminomethyl-1'-pyridinium)-3-(4'-carbamoyl-1-pyridinium)). In addition, we interrogated an 840-member novel oxime library for reactivation of Y337A/F338A hAChE-OP conjugates to delineate the most efficient oxime-mutant enzyme pairs for catalytic bio-scavenging. Combining the increased accessibility of the Y337A mutation to oximes within the space-impacted active center gorge with the aging resistance of the F338A mutation provides increased substrate diversity in scavenging potential for aging-prone alkyl phosphate inhibitors.
Topics: Acetylcholinesterase; Aging; Catalytic Domain; Humans; Mutation, Missense; Organophosphates; Oximes; Pyridinium Compounds
PubMed: 21730071
DOI: 10.1074/jbc.M111.264739 -
International Journal of Molecular... Oct 2022In the present study, four -substituted oximes of quinuclidin-3-one were synthesized using appropriate -substituted hydroxylamine hydrochlorides. In order to perform...
In the present study, four -substituted oximes of quinuclidin-3-one were synthesized using appropriate -substituted hydroxylamine hydrochlorides. In order to perform these reactions in a solvent, a mixture of () and () products was yielded. Using mechanochemical and microwave synthesis, we then obtained pure () oximes. In almost all cases, the conversion to oxime ethers was completed. Reactions were monitored by ATR spectroscopy and the ratios of () and () oxime ethers were deduced from H NMR data. Several reactions were very rapid (1 min) with 100% conversion and stereospecificity. To investigate the reaction mechanisms, full conformational analyses of the reaction intermediates were performed and the lowest energy conformers were determined. These conformers differed in spatial arrangement around the nitrogen atom of the amino group and were in the correct orientation for reactions to occur. Calculated standard Gibbs energies of the formation were in agreement with the experimentally obtained ratios of ( and () isomers. This work shows alternatives to the classical synthesis of -substituted oxime ether precursors and highlights the fast reaction rate and stereoselectivity of microwave synthesis as well as the "green" aspects of mechanochemistry.
Topics: Oximes; Ether; Ethers; Nitrogen; Solvents
PubMed: 36293187
DOI: 10.3390/ijms232012331