Acetylcholinesterase

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Kamil Kuca - One of the best experts on this subject based on the ideXlab platform.

  • a comparison of reactivating and therapeutic efficacy of bispyridinium Acetylcholinesterase reactivator kr 22934 with the oxime k203 and commonly used oximes obidoxime trimedoxime hi 6 in tabun poisoned rats and mice
    Toxicology Mechanisms and Methods, 2011
    Co-Authors: Jiri Kassa, Jiri Bajgar, Jana Žďárová Karasová, Kamil Kuca, Kamil Musilek, Růžena Pavlíková, Youngsik Jung
    Abstract:

    The potency of bispyridinium Acetylcholinesterase reactivator KR-22934 in reactivating tabun-inhibited Acetylcholinesterase and reducing tabun-induced lethal toxic effects was compared with the oxime K203 and commonly used oximes. Studies determining percentage of reactivation of tabun-inhibited blood and tissue Acetylcholinesterase in rats showed that the reactivating efficacy of KR-22934 was slightly higher than the reactivating efficacy of K203 and roughly corresponded to the reactivating efficacy of obidoxime and trimedoxime in blood and diaphragm. On the other hand, the oxime KR-22934 was not able to reactivate tabun-inhibited Acetylcholinesterase in the brain. The therapeutic efficacy of all oximes studied approximately corresponded to their reactivating efficacy. Based on the results, one can conclude that the oxime KR-22934 is not suitable for the replacement of commonly used oximes for the antidotal treatment of tabun poisoning in spite of its potency to reactivate tabun-inhibited Acetylcholinesterase in the peripheral compartment (blood, diaphragm).

  • in vitro oxime assisted reactivation of paraoxon inhibited human Acetylcholinesterase and butyrylcholinesterase
    Clinical Toxicology, 2009
    Co-Authors: Lucie Musilova, Kamil Kuca, Youngsik Jung, Daniel Jun
    Abstract:

    Introduction. Organophosphorus pesticides and nerve agents are highly toxic to humans and other living organisms, primarily because of their interaction with enzyme Acetylcholinesterase. The aim of our study was to find suitable reactivators of Acetylcholinesterase and butyrylcholinesterase and to recommend the most efficacious compounds for the next evaluation as antidotes for intoxication by pesticides.  Methods. Eighteen structurally different oxime reactivators were tested for their in vitro ability to reactivate paraoxon-inhibited human erythrocyte Acetylcholinesterase and human plasma butyrylcholinesterase to find out structure–activity relationship within this set of compounds. Their reactivation ability was compared with commercially available Acetylcholinesterase reactivators (pralidoxime, methoxime, trimedoxime, obidoxime, and HI-6). Results and discussion. The best reactivation ability was achieved with obidoxime, trimedoxime, compounds K027, K075, K203, and K048. We have also tested reactivati...

  • Effect of Several New and Currently Available Oxime Cholinesterase Reactivators on Tabun-intoxicated Rats
    International journal of molecular sciences, 2008
    Co-Authors: Jana Žďárová Karasová, Jiri Kassa, Miroslav Pohanka, Kamil Musilek, Youngsik Jung, Kamil Kuca
    Abstract:

    The therapeutical efficacies of eleven oxime-based Acetylcholinesterase reactivators were compared in an in vivo (rat model) study of treatment of intoxication caused by tabun. In this group there were some currently available oximes (obidoxime, trimedoxime and HI-6) and the rest were newly synthesized compounds. The best reactivation efficacy for Acetylcholinesterase in blood (expressed as percent of reactivation) among the currently available oximes was observed after administration of trimedoxime (16%) and of the newly synthesized K127 (22432) (25%). The reactivation of butyrylcholinesterase in plasma was also studied; the best reactivators were trimedoxime, K117 (22435), and K127 (22432), with overall reactivation efficacies of approximately 30%. Partial protection of brain ChE against tabun inhibition was observed after administration of trimedoxime (Acetylcholinesterase 20%; butyrylcholinesterase 30%) and obidoxime (Acetylcholinesterase 12%; butyrylcholinesterase 16%).

  • a comparison of reactivating efficacy of newly developed oximes k074 k075 and currently available oximes obidoxime hi 6 in soman cyclosarin and tabun poisoned rats
    Chemico-Biological Interactions, 2008
    Co-Authors: Jiri Kassa, Jiri Bajgar, Jana Žďárová Karasová, Daniel Jun, Kamil Kuca
    Abstract:

    The potency of newly developed oximes (K074, K075) and commonly used oximes (obidoxime, HI-6) to reactivate nerve agent-inhibited Acetylcholinesterase was evaluated in rats poisoned with soman, tabun or cyclosarin at a lethal dose corresponding to their LD(50) value. In vivo determined percentage of reactivation of soman-inhibited blood and brain Acetylcholinesterase in poisoned rats showed that only the oxime HI-6 was able to reactivate soman-inhibited Acetylcholinesterase in the peripheral (blood) as well as central (brain) compartment. In vivo determined percentage of reactivation of tabun-inhibited blood and brain Acetylcholinesterase in poisoned rats showed that obidoxime is the most efficacious reactivator of tabun-inhibited Acetylcholinesterase among studied oximes in the peripheral compartment (blood) while K074 seems to be the most efficacious reactivator of tabun-inhibited Acetylcholinesterase among studied oximes in the central compartment (brain). In vivo determined percentage of reactivation of cyclosarin-inhibited blood and brain Acetylcholinesterase in poisoned rats showed that HI-6 is the most efficacious reactivator of cyclosarin-inhibited Acetylcholinesterase among studied oximes. Due to their reactivating effects, both newly developed K oximes can be considered to be promising oximes for the antidotal treatment of acute tabun poisonings while the oxime HI-6 is still the most promising oxime for the treatment of acute soman and cyclosarin poisonings.

  • Article Effect of Several New and Currently Available Oxime
    2008
    Co-Authors: Cholinesterase Reactivators, Jana Žďárová Karasová, Jiri Kassa, Miroslav Pohanka, Kamil Musilek, Youngsik Jung, Tabun-intoxicated Rats, Kamil Kuca
    Abstract:

    Abstract: The therapeutical efficacies of eleven oxime-based Acetylcholinesterase reactivators were compared in an in vivo (rat model) study of treatment of intoxication caused by tabun. In this group there were some currently available oximes (obidoxime, trimedoxime and HI-6) and the rest were newly synthesized compounds. The best reactivation efficacy for Acetylcholinesterase in blood (expressed as percent of reactivation) among the currently available oximes was observed after administration of trimedoxime (16%) and of the newly synthesized K127 (22432) (25%). The reactivation of butyrylcholinesterase in plasma was also studied; the best reactivators were trimedoxime, K117 (22435), and K127 (22432), with overall reactivation efficacies of approximately 30%. Partial protection of brain ChE against tabun inhibition was observed after administration of trimedoxime (Acetylcholinesterase 20%; butyrylcholinesterase 30%) and obidoxime (Acetylcholinesterase 12%

Jiri Kassa - One of the best experts on this subject based on the ideXlab platform.

  • a comparison of the reactivating and therapeutic efficacy of two novel bispyridinium oximes k727 k733 with the oxime hi 6 and obidoxime in sarin poisoned rats and mice
    Toxicology Mechanisms and Methods, 2015
    Co-Authors: Jiri Kassa, Vendula Sepsova, Lenka Matouskova, Anna Horova, Kamil Musilek
    Abstract:

    AbstractThe ability of two novel bispyridinium oximes K727 and K733 and currently available oximes (HI-6, obidoxime) to reactivate sarin-inhibited Acetylcholinesterase and to reduce acute toxicity of sarin was evaluated. To investigate the reactivating efficacy of the oximes, the rats were administered intramuscularly with atropine and oximes in equitoxic doses corresponding to 5% of their LD50 values at 1 min after the intramuscular administration of sarin at a dose of 24 µg/kg (LD50). The activity of Acetylcholinesterase was measured at 60 min after sarin poisoning. The LD50 value of sarin in non-treated and treated mice was assessed using probit-logarithmical analysis of death occurring within 24 h after intramuscular administration of sarin at five different doses. In vivo determined percentage of reactivation of sarin-inhibited rat blood, diaphragm and brain Acetylcholinesterase showed that the potency of both novel oximes K727 and K733 to reactivate sarin-inhibited Acetylcholinesterase roughly corre...

  • a comparison of reactivating and therapeutic efficacy of bispyridinium Acetylcholinesterase reactivator kr 22934 with the oxime k203 and commonly used oximes obidoxime trimedoxime hi 6 in tabun poisoned rats and mice
    Toxicology Mechanisms and Methods, 2011
    Co-Authors: Jiri Kassa, Jiri Bajgar, Jana Žďárová Karasová, Kamil Kuca, Kamil Musilek, Růžena Pavlíková, Youngsik Jung
    Abstract:

    The potency of bispyridinium Acetylcholinesterase reactivator KR-22934 in reactivating tabun-inhibited Acetylcholinesterase and reducing tabun-induced lethal toxic effects was compared with the oxime K203 and commonly used oximes. Studies determining percentage of reactivation of tabun-inhibited blood and tissue Acetylcholinesterase in rats showed that the reactivating efficacy of KR-22934 was slightly higher than the reactivating efficacy of K203 and roughly corresponded to the reactivating efficacy of obidoxime and trimedoxime in blood and diaphragm. On the other hand, the oxime KR-22934 was not able to reactivate tabun-inhibited Acetylcholinesterase in the brain. The therapeutic efficacy of all oximes studied approximately corresponded to their reactivating efficacy. Based on the results, one can conclude that the oxime KR-22934 is not suitable for the replacement of commonly used oximes for the antidotal treatment of tabun poisoning in spite of its potency to reactivate tabun-inhibited Acetylcholinesterase in the peripheral compartment (blood, diaphragm).

  • Effect of Several New and Currently Available Oxime Cholinesterase Reactivators on Tabun-intoxicated Rats
    International journal of molecular sciences, 2008
    Co-Authors: Jana Žďárová Karasová, Jiri Kassa, Miroslav Pohanka, Kamil Musilek, Youngsik Jung, Kamil Kuca
    Abstract:

    The therapeutical efficacies of eleven oxime-based Acetylcholinesterase reactivators were compared in an in vivo (rat model) study of treatment of intoxication caused by tabun. In this group there were some currently available oximes (obidoxime, trimedoxime and HI-6) and the rest were newly synthesized compounds. The best reactivation efficacy for Acetylcholinesterase in blood (expressed as percent of reactivation) among the currently available oximes was observed after administration of trimedoxime (16%) and of the newly synthesized K127 (22432) (25%). The reactivation of butyrylcholinesterase in plasma was also studied; the best reactivators were trimedoxime, K117 (22435), and K127 (22432), with overall reactivation efficacies of approximately 30%. Partial protection of brain ChE against tabun inhibition was observed after administration of trimedoxime (Acetylcholinesterase 20%; butyrylcholinesterase 30%) and obidoxime (Acetylcholinesterase 12%; butyrylcholinesterase 16%).

  • a comparison of reactivating efficacy of newly developed oximes k074 k075 and currently available oximes obidoxime hi 6 in soman cyclosarin and tabun poisoned rats
    Chemico-Biological Interactions, 2008
    Co-Authors: Jiri Kassa, Jiri Bajgar, Jana Žďárová Karasová, Daniel Jun, Kamil Kuca
    Abstract:

    The potency of newly developed oximes (K074, K075) and commonly used oximes (obidoxime, HI-6) to reactivate nerve agent-inhibited Acetylcholinesterase was evaluated in rats poisoned with soman, tabun or cyclosarin at a lethal dose corresponding to their LD(50) value. In vivo determined percentage of reactivation of soman-inhibited blood and brain Acetylcholinesterase in poisoned rats showed that only the oxime HI-6 was able to reactivate soman-inhibited Acetylcholinesterase in the peripheral (blood) as well as central (brain) compartment. In vivo determined percentage of reactivation of tabun-inhibited blood and brain Acetylcholinesterase in poisoned rats showed that obidoxime is the most efficacious reactivator of tabun-inhibited Acetylcholinesterase among studied oximes in the peripheral compartment (blood) while K074 seems to be the most efficacious reactivator of tabun-inhibited Acetylcholinesterase among studied oximes in the central compartment (brain). In vivo determined percentage of reactivation of cyclosarin-inhibited blood and brain Acetylcholinesterase in poisoned rats showed that HI-6 is the most efficacious reactivator of cyclosarin-inhibited Acetylcholinesterase among studied oximes. Due to their reactivating effects, both newly developed K oximes can be considered to be promising oximes for the antidotal treatment of acute tabun poisonings while the oxime HI-6 is still the most promising oxime for the treatment of acute soman and cyclosarin poisonings.

  • Article Effect of Several New and Currently Available Oxime
    2008
    Co-Authors: Cholinesterase Reactivators, Jana Žďárová Karasová, Jiri Kassa, Miroslav Pohanka, Kamil Musilek, Youngsik Jung, Tabun-intoxicated Rats, Kamil Kuca
    Abstract:

    Abstract: The therapeutical efficacies of eleven oxime-based Acetylcholinesterase reactivators were compared in an in vivo (rat model) study of treatment of intoxication caused by tabun. In this group there were some currently available oximes (obidoxime, trimedoxime and HI-6) and the rest were newly synthesized compounds. The best reactivation efficacy for Acetylcholinesterase in blood (expressed as percent of reactivation) among the currently available oximes was observed after administration of trimedoxime (16%) and of the newly synthesized K127 (22432) (25%). The reactivation of butyrylcholinesterase in plasma was also studied; the best reactivators were trimedoxime, K117 (22435), and K127 (22432), with overall reactivation efficacies of approximately 30%. Partial protection of brain ChE against tabun inhibition was observed after administration of trimedoxime (Acetylcholinesterase 20%; butyrylcholinesterase 30%) and obidoxime (Acetylcholinesterase 12%

Xuejun Zhang - One of the best experts on this subject based on the ideXlab platform.

  • the ccaat binding factor cbf nf y regulates the human Acetylcholinesterase promoter activity during calcium ionophore a23187 induced cell apoptosis
    Biochimica et Biophysica Acta, 2007
    Co-Authors: Hui Zhu, Wei Gao, Yufang Shi, Xuejun Zhang
    Abstract:

    We previously reported that the expression of Acetylcholinesterase during A23187-induced apoptosis of HeLa cells is regulated by Ca(2+) mobilization through the modulation of mRNA stability and Acetylcholinesterase promoter activity. Transactivation of the human Acetylcholinesterase promoter by A23187 was partially mediated by the distal CCAAT motif within the -1270 to -1248 fragment of the human Acetylcholinesterase promoter, which was bound by the CCAAT binding factor (CBF/NF-Y). In the present study, we investigated the molecular mechanisms by which CBF/NF-Y regulates A23187-induced activation of the human Acetylcholinesterase promoter. The results indicate that CBF/NF-Y binding to the distal CCAAT motif suppresses the promoter activity. Electrophoretic mobility shift assays (EMSAs) demonstrated that binding of CBF/NF-Y to the distal CCAAT motif decreased after A23187 treatment. Our results suggest that Acetylcholinesterase promoter activation during A23187-induced HeLa cell apoptosis may result partly from the dissociation of CBF/NF-Y from the distal CCAAT motif in the Acetylcholinesterase promoter, reversing this suppression.

  • calcineurin mediates Acetylcholinesterase expression during calcium ionophore a23187 induced hela cell apoptosis
    Biochimica et Biophysica Acta, 2007
    Co-Authors: Hui Zhu, Wei Gao, Yufang Shi, Hua Jiang, Xuejun Zhang
    Abstract:

    We previously reported that Acetylcholinesterase plays a critical role in apoptosis and its expression is regulated by Ca(2+) mobilization. In the present study, we show that activated calpain, a cytosolic calcium-activated cysteine protease, and calcineurin, a calcium-dependent protein phosphatase, regulate Acetylcholinesterase expression during A23187-induced apoptosis. The calpain inhibitor, calpeptin, and the calcineurin inhibitors, FK506 and cyclosporine A, inhibited Acetylcholinesterase expression at both mRNA and protein levels and suppressed the activity of the human Acetylcholinesterase promoter. In contrast, overexpression of constitutively active calcineurin significantly activated the Acetylcholinesterase promoter. Furthermore, we identify a role for the transcription factor NFAT (nuclear factor of activated T cells), a calcineurin target, in regulating the Acetylcholinesterase promoter during ionophore-induced apoptosis. Overexpression of human NFATc3 and NFATc4 greatly increased the Acetylcholinesterase promoter activity in HeLa cells treated with A23187. Overexpression of constitutive nuclear NFATc4 activated the Acetylcholinesterase promoter independent of A23187, whereas overexpression of dominant-negative NFAT blocked A23187-induced Acetylcholinesterase promoter activation. These results indicate that calcineurin mediates Acetylcholinesterase expression during apoptosis.

  • regulation of Acetylcholinesterase expression by calcium signaling during calcium ionophore a23187 and thapsigargin induced apoptosis
    The International Journal of Biochemistry & Cell Biology, 2007
    Co-Authors: Hui Zhu, Wei Gao, Yufang Shi, Hua Jiang, Qihuang Jin, Karl Wah Keung Tsim, Xuejun Zhang
    Abstract:

    We have recently reported that Acetylcholinesterase expression was induced during apoptosis in various cell types. In the current study we provide evidence to suggest that the induction of Acetylcholinesterase expression during apoptosis is regulated by the mobilization of intracellular Ca(2+). During apoptosis, treatment of HeLa and MDA-MB-435s cells with the calcium ionophore A23187 resulted in a significant increase in Acetylcholinesterase mRNA and protein levels. Chelation of intracellular Ca(2+) by BAPTA-AM (1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester), an intracellular Ca(2+) chelator, inhibited Acetylcholinesterase expression. A23187 also enhanced the stability of Acetylcholinesterase mRNA and increased the activity of Acetylcholinesterase promoter, effects that were blocked by BAPTA-AM. Perturbations of cellular Ca(2+) homeostasis by thapsigargin resulted in the increase of Acetylcholinesterase expression as well as Acetylcholinesterase promoter activity during thapsigargin induced apoptosis in HeLa and MDA-MB-435s cells, effects that were also inhibited by BAPTA-AM. We further demonstrated that the transactivation of the human Acetylcholinesterase promoter by A23187 and thapsigargin was partially mediated by a CCAAT motif within the -1270 to -1248 fragment of the human Acetylcholinesterase promoter. This motif was able to bind to CCAAT binding factor (CBF/NF-Y). These results strongly suggest that cytosolic Ca(2+) plays a key role in Acetylcholinesterase regulation during apoptosis induced by A23187 and thapsigargin.

Daniel Jun - One of the best experts on this subject based on the ideXlab platform.

  • in vitro oxime assisted reactivation of paraoxon inhibited human Acetylcholinesterase and butyrylcholinesterase
    Clinical Toxicology, 2009
    Co-Authors: Lucie Musilova, Kamil Kuca, Youngsik Jung, Daniel Jun
    Abstract:

    Introduction. Organophosphorus pesticides and nerve agents are highly toxic to humans and other living organisms, primarily because of their interaction with enzyme Acetylcholinesterase. The aim of our study was to find suitable reactivators of Acetylcholinesterase and butyrylcholinesterase and to recommend the most efficacious compounds for the next evaluation as antidotes for intoxication by pesticides.  Methods. Eighteen structurally different oxime reactivators were tested for their in vitro ability to reactivate paraoxon-inhibited human erythrocyte Acetylcholinesterase and human plasma butyrylcholinesterase to find out structure–activity relationship within this set of compounds. Their reactivation ability was compared with commercially available Acetylcholinesterase reactivators (pralidoxime, methoxime, trimedoxime, obidoxime, and HI-6). Results and discussion. The best reactivation ability was achieved with obidoxime, trimedoxime, compounds K027, K075, K203, and K048. We have also tested reactivati...

  • a comparison of reactivating efficacy of newly developed oximes k074 k075 and currently available oximes obidoxime hi 6 in soman cyclosarin and tabun poisoned rats
    Chemico-Biological Interactions, 2008
    Co-Authors: Jiri Kassa, Jiri Bajgar, Jana Žďárová Karasová, Daniel Jun, Kamil Kuca
    Abstract:

    The potency of newly developed oximes (K074, K075) and commonly used oximes (obidoxime, HI-6) to reactivate nerve agent-inhibited Acetylcholinesterase was evaluated in rats poisoned with soman, tabun or cyclosarin at a lethal dose corresponding to their LD(50) value. In vivo determined percentage of reactivation of soman-inhibited blood and brain Acetylcholinesterase in poisoned rats showed that only the oxime HI-6 was able to reactivate soman-inhibited Acetylcholinesterase in the peripheral (blood) as well as central (brain) compartment. In vivo determined percentage of reactivation of tabun-inhibited blood and brain Acetylcholinesterase in poisoned rats showed that obidoxime is the most efficacious reactivator of tabun-inhibited Acetylcholinesterase among studied oximes in the peripheral compartment (blood) while K074 seems to be the most efficacious reactivator of tabun-inhibited Acetylcholinesterase among studied oximes in the central compartment (brain). In vivo determined percentage of reactivation of cyclosarin-inhibited blood and brain Acetylcholinesterase in poisoned rats showed that HI-6 is the most efficacious reactivator of cyclosarin-inhibited Acetylcholinesterase among studied oximes. Due to their reactivating effects, both newly developed K oximes can be considered to be promising oximes for the antidotal treatment of acute tabun poisonings while the oxime HI-6 is still the most promising oxime for the treatment of acute soman and cyclosarin poisonings.

  • amperometric biosensor for evaluation of competitive cholinesterase inhibition by the reactivator hi 6
    Analytical Letters, 2007
    Co-Authors: Miroslav Pohanka, Daniel Jun, Kamil Kuca
    Abstract:

    Abstract Amperometric biosensors containing enzymes butyrylcholinesterase or Acetylcholinesterase were prepared. The biosensors were employed for studying of cholinesterase reactivator: HI‐6. Competitions between HI‐6 and acetylthiocholine as enzyme substrate were used for determination of IC50 value. Biosensors with butyrylcholinesterase from human serum determined IC50 as (1.00±0.02)×10−6 M; the biosensor with Acetylcholinesterase from human erythrocytes performance provided IC50 (3.31±0.13)×10−6 M, the one with human recombinant Acetylcholinesterase (2.00±0.06)×10−6 M and finally biosensor with Acetylcholinesterase from electric eel (6.17±0.17)×10−6 M when 5 mM acetylthiocholine as substrate was used. We are encouraged to consider presented biosensors as a very useful for evaluation of newly prepared cholinesterase reactivators.

  • bispyridinium oximes as antidotal treatment of cyclosarin poisoning in vitro and in vivo testing
    International Journal of Toxicology, 2005
    Co-Authors: L. Bartosova, Kamil Kuca, Daniel Jun, G. Kunesova
    Abstract:

    The mechanism of intoxication with organophosphorus compounds, including highly toxic nerve agents and less toxic pesticides, is based on the formation of irreversibly inhibited Acetylcholinesterase, which causes cumulation of neuromediator acetylcholine in synaptic clefts and subsequent overstimulation of cholinergic receptors, that is followed by a generalized cholinergic crisis. Nerve agent poisoning is conventionally treated using a combination of a cholinolytic (atropine mostly) to counteract the accumulation of acetylcholine and Acetylcholinesterase reactivators (pralidoxime or obidoxime) to reactivate inhibited Acetylcholinesterase. In this study of cyclosarin poisoning treatment, oximes of different chemical structures (obidoxime, HI-6, BI-6, and HS-6) were tested in vitro on rat brain Acetylcholinesterase (enzyme source: rat brain homogenate), and afterwards, they were tested in vivo in equimolar doses, in mice and rats. The HI-6 oxime appeared to be the most effective oxime in vitro and in vivo.

Bhupendra P Doctor - One of the best experts on this subject based on the ideXlab platform.

  • differences in active site gorge dimensions of cholinesterases revealed by binding of inhibitors to human butyrylcholinesterase
    Chemico-Biological Interactions, 1999
    Co-Authors: Ashima Saxena, Oksana Lockridge, Ann M G Redman, Xuliang Jiang, Bhupendra P Doctor
    Abstract:

    Amino acid sequence alignments of cholinesterases revealed that 6 of 14 aromatic amino acid residues lining the active center gorge of Acetylcholinesterase are replaced by aliphatic amino acid residues in butyrylcholinesterase. The Y337(F330) in mammalian Acetylcholinesterase, which is replaced by A328 in human butyrylcholinesterase, is implicated in the binding of ligands such as huperzine A, edrophonium, and acridines and one end of bisquaternary compounds such as BW284C51 and decamethonium. Y337 may sterically hinder the binding of phenothiazines such as ethopropazine, which contains a bulky exocyclic substitution. Inhibition studies of (−)-huperzine A with human butyrylcholinesterase mutants, where A328 (KI = 194.6 μM) was modified to either F (KI = 0.6 μM, as in Torpedo Acetylcholinesterase) or Y (KI = 0.032 μM, as in mammalian Acetylcholinesterase), confirmed previous observations made with Acetylcholinesterase mutants that this residue is important for binding huperzine A. Inhibition studies of eth...

  • differences in active site gorge dimensions of cholinesterases revealed by binding of inhibitors to human butyrylcholinesterase
    Biochemistry, 1997
    Co-Authors: Ashima Saxena, Oksana Lockridge, Ann M G Redman, Xuliang Jiang, Bhupendra P Doctor
    Abstract:

    Amino acid sequence alignments of cholinesterases revealed that 6 of 14 aromatic amino acid residues lining the active center gorge of Acetylcholinesterase are replaced by aliphatic amino acid residues in butyrylcholinesterase. The Y337 (F330) in mammalian Acetylcholinesterase, which is replaced by A328 in human butyrylcholinesterase, is implicated in the binding of ligands such as huperzine A, edrophonium, and acridines and one end of bisquaternary compounds such as BW284C51 and decamethonium. Y337 may sterically hinder the binding of phenothiazines such as ethopropazine, which contains a bulky exocyclic substitution. Inhibition studies of (-)-huperzine A with human butyrylcholinesterase mutants, where A328 (KI = 194.6 microM) was modified to either F (KI = 0.6 microM, as in Torpedo Acetylcholinesterase) or Y (KI = 0.032 microM, as in mammalian Acetylcholinesterase), confirmed previous observations made with Acetylcholinesterase mutants that this residue is important for binding huperzine A. Inhibition studies of ethopropazine with butyrylcholinesterase mutants, where A328 (KI = 0.18 microM) was modified to either F (KI = 0.82 microM) or Y (KI = 0.28 microM), suggested that A328 was not solely responsible for the selectivity of ethopropazine. Volume calculations for the active site gorge showed that the poor inhibitory activity of ethopropazine toward Acetylcholinesterase was due to the smaller dimension of the active site gorge which was unable to accommodate the bulky inhibitor molecule. The volume of the butyrylcholinesterase active site gorge is approximately 200 A3 larger than that of the Acetylcholinesterase gorge, which allows the accommodation of ethopropazine in two different orientations as demonstrated by rigid-body refinement and molecular dynamics calculations.