Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.1.7 (acetylcholinesterase)
28,390 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A series of structurally related monosubstituted 1-[(alkenyloxy)methyl]-, 1-[(alkynyloxy)methyl]-, and 1-[(aralkyloxy)methyl]-2-[(hydroxyimino)methyl]-3-methyli midazolium halides were prepared and evaluated. All new compounds were characterized with respect to (hydroxyimino)methyl acid dissociation constant, nucleophilicity, and octanol-buffer partition coefficient. The alkynyloxy-substituted compounds were also evaluated in vitro with respect to reversible inhibition of human erythrocyte (RBC) acetylcholinesterase (AChE) and kinetics of reactivation of human AChE inhibited by ethyl p-nitrophenyl methylphosphonate (EPMP). In vivo evaluation in mice revealed that coadministration of alkynyloxy-substituted imidazolium compounds with atropine sulfate provided significant protection against a 2 x LD50 challenge of GD. For the alkynyloxy-substituted imidazolium drugs there is a direct relationship between in vitro and in vivo activity: the most potent in vivo compounds against GD proved to be potent in vitro reactivators against EPMP-inhibited human AChE. These results differ from the observations made on the sterically hindered imidazolium compounds (see previous article) and suggest that several antidotal mechanisms of protective action may be applicable for the imidazolium aldoxime family of therapeutics. The ability of the alkynyloxy substituents to provide life-saving protection against GD intoxication was not transferable to the pyridinium or triazolium heteroaromatic ring systems.
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PMID:Quaternary salts of 2-[(hydroxyimino)methyl]imidazole. 3. Synthesis and evaluation of (alkenyloxy)-, (alkynyloxy)-, and (aralkyloxy)methyl quaternarized 2-[(hydroxyimino)methyl]-1-alkylimidazolium halides as reactivators and therapy for soman intoxication. 291 11

We have previously communicated that heparan sulfate and heparin released 16S acetylcholinesterase (AChE) from cholinergic synapses. These experiments suggest that heparan-like molecules are involved in the anchorage of AChE to the neuromuscular junction. In order to prove the in vivo interaction between the 16S AChE and heparan sulfate residues, the binding of exogenously added 16S enzyme to intact cells rich in cell-surface heparan sulfate proteoglycans was examined; 16S AChE form was shown to bind to intact endothelial cells in a specific, time-dependent, saturable fashion. A single class of binding sites was involved and at saturation around 2.52 X 10(11) molecules of 16S AChE/cm2 were bound. Fifty percent of the binding of the 16S AChE was blocked by heparan sulfate, heparin, or previous treatment of the cell with heparitinase. The binding was reversed by exogenous heparin, but not by chondroitin sulfate or hyaluronic acid. Our results demonstrate that the synaptic form of AChE binds to heparan sulfate proteoglycans on the surface of the cell.
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PMID:The synaptic form of acetylcholinesterase binds to cell-surface heparan sulfate proteoglycans. 293 28

Experiments were designed to study functional associations of proteins in human red cell membranes as the membranes are induced to undergo the critical membrane events of invagination or evagination followed by constriction and fusion. Three examples were chosen for study: the inside-out vesicle (IOV) produced in white ghosts by hypotonic removal of cytoskeletal proteins; the endocytic vacuole produced in white ghosts by incubation with Mg-adenosine triphosphate; and the exocytic vesicle produced by metabolic depletion of intact red blood cells. The resulting particles were harvested, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for membrane protein content and by enzymic analysis to detect the presence or absence of the exofacial enzyme acetylcholinesterase (ACE), the cytosol facing enzyme glyceraldehyde phosphate dehydrogenase (GAPD), and the integral protein adenosine triphosphatases (ATPases). Each of the vesicles is variably depleted of spectrin and actin, and each retains the exofacial enzyme ACE as well as Mg-ATPase. These findings suggest that there must be local partial depletion of cytoskeletal proteins before invagination or evagination occurs and that in each case part of the exoface of the membrane containing ACE is carried along into the resulting vesicle. The two forms of endocytosis differ with regard to their ATPase content with the energized endocytic vacuole retaining Ca-Mg-ATPase and actin-activated ATPase. The large amount of hemoglobin present in the exocytic vesicle is best explained by trapping of free cytosol and probably reflects a direct interaction of cytosolic components containing hemoglobin with the phospholipid bilayer.
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PMID:Endo- and exovesiculation and the structure of the human red cell membrane. 294 77

We have previously shown that asymmetric collagen-tailed acetylcholinesterase (AChE) is anchored to the extracellular matrix (ECM) by heparan sulfate proteoglycans (HSPGs). Here we present our studies on the characterization of such PGs from the ECM of rat skeletal muscles. After radiolabeling with 35SO4 for 24h, PGs were extracted from the muscle ECM with 4.0 M guanidine-HCl containing protease inhibitors. PGs were subsequently isolated using sequential DEAE-Sephacel chromatography, digestion with chondroitinase ABC, and Sepharose CL-4B. Two different hydrodynamic size species of HSPGs were found. One type had a Mr of 4-6 X 10(5) (Kav = 0.25) as estimated by gel chromatography in the presence of 1% SDS and accounted for 75% of the total HSPGs. The other HSPG had a Mr 1.5-2.5 X 10(5) (Kav = 0.41). The glycosaminoglycan (GAG) side chains (Mr 20,000 and 12,000) were found composed only of heparan sulfate as determined by nitrous acid oxidation and heparitinase treatment. The large-sized HSPG, which is concentrated in synaptic regions, contains only GAG chains of Mr 20,000, suggesting that each HSPG contains only one kind of heparan sulfate chain in its structure. Our results definitively establish by biochemical criteria that the basement membrane of mammalian skeletal muscle contains HSPGs, the likely matrix receptor for the immobilization of the asymmetric collagen-tailed AChE at the neuromuscular junction.
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PMID:Isolation of the heparan sulfate proteoglycans from the extracellular matrix of rat skeletal muscle. 295 79

Acetylcholinesterase (AchE: EC 3.1.1.7) was identified and purified from the hemolymph of the scorpion Heterometrus bengalensis. The purity of the enzyme was determined by polyacrylamide gel electrophoresis (PAGE). The molecular weight of the enzyme, determined by sodium dodecyl sulfate-PAGE, was 80,000. The purified AchE hydrolysed acetylthiocholine iodide, but it did not react with butyrylthiocholine iodide. BW284C51, a specific inhibitor of AchE, strongly inhibited the enzyme. The known inhibitor (tetramonoisopropylpyrophosphortetramide) of pseudocholinesterase did not produce any inhibition of the enzyme activity. The purified AchE of scorpion hemolymph was vulnerable to high substrate concentration. The presence of Cu2+ and Ni2+ reduced the enzyme activity, whereas the metal ion, Sn2+, enhanced AchE activity. Ca2+ produced neither inhibition nor activation. (Na+, K+)-ATPase and Mg2+-ATPase activities were greatly enhanced by the purified AchE.
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PMID:Acetylcholinesterase (EC 3.1.1.7), a neurotransmitter enzyme in scorpion hemolymph. 296 37

The presence of a glycoinositol phospholipid anchor in Drosophila acetylcholinesterase (AChE) was shown by several criteria. Chemical analysis of highly purified Drosophila AChE demonstrated approximately one residue of inositol per enzyme subunit. Selective cleavage by Staphylococcus aureus phosphatidylinositol-specific phospholipase C (PI-PLC) was tested with Drosophila AChE radiolabeled by the photoactivatable affinity probe 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine [( 125I]TID), a reagent that specifically labels the lipid moiety of glycoinositol phospholipid-anchored proteins. Digestion with PI-PLC released 75% of this radiolabel from the protein. Gel electrophoresis of Drosophila AChE in sodium dodecyl sulfate indicated prominent 55- and 16-kDa bands and a faint 70-kDa band. The [125I]TID label was localized on the 55-kDa fragment, suggesting that this fragment is the C-terminal portion of the protein. In support of this conclusion, a sensitive microsequencing procedure that involved manual Edman degradation combined with radiomethylation was used to determine residues 2-5 of the 16-kDa fragment. Comparison with the Drosophila AChE cDNA sequence [Hall, L.M.C., & Spierer, P. (1986) EMBO J. 5, 2949-2954] confirmed that the 16-kDa fragment includes the N-terminus of AChE. Furthermore, the position of the N-terminal amino acid of the mature Drosophila AChE is closely homologous to that of Torpedo AChE. The presence of radiomethylatable ethanolamine in both 16- and 55-kDa fragments was also confirmed. Thus, Drosophila AChE may include a second posttranslational modification involving ethanolamine.
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PMID:Drosophila acetylcholinesterase: demonstration of a glycoinositol phospholipid anchor and an endogenous proteolytic cleavage. 297 7

Conotoxin GI, a peptide neurotoxin contained in the venom of the marine snail Conus geographus, was applied to the cutaneous pectoris muscle of the frog, and the effects on the postsynaptic response to acetylcholine were examined. Conotoxin GI reversibly blocked nerve-evoked muscle contractions at concentrations greater than or equal to 3 to 4 microM. Micromolar concentrations of conotoxin GI significantly reduced the amplitude of miniature endplate potentials and membrane depolarizations produced by ionophoretic application of acetylcholine, suggesting that the toxin reduced the postsynaptic sensitivity to acetylcholine. The reduction in the sensitivity of the muscle to acetylcholine was not due to changes in muscle fiber resting membrane potential or input resistance. Conotoxin GI reduced the amplitudes but did not affect the rates of decay of focal, extracellularly recorded endplate currents or miniature endplate currents, suggesting that the toxin did not affect the lifetime of ion channels opened by acetylcholine. Miniature endplate currents decay five to six times more slowly than normal when acetylcholinesterase is blocked with neostigmine methyl sulfate due to repeated binding of acetylcholine to receptors as it diffuses from the synaptic cleft. Conotoxin GI reduced the amplitude and increased the rate of decay of miniature endplate currents recorded in the presence of neostigmine methyl sulfate, suggesting that the toxin reduced the binding of acetylcholine to endplate receptors. These results are consistent with the hypothesis that conotoxin GI blocks neuromuscular transmission at the frog endplate by reducing the binding of acetylcholine to receptors.
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PMID:Postsynaptic block of frog neuromuscular transmission by conotoxin GI. 298 Dec 95

The asymmetric forms of acetylcholinesterase were purified from the electric organs of the electric rays Narke japonica and Torpedo californica, and their properties were compared. Asymmetric acetylcholinesterase was purified by immunoaffinity chromatography with a monoclonal antibody (Nj-601) to acetylcholinesterase. The MgCl2 extracts of these electric organs were applied to a column of Nj-601-Sepharose, and the bound acetylcholinesterase was eluted by lowering the pH of the eluent to 2.8. The purified asymmetric acetylcholinesterases gave peaks of 17 S (A12) and 13 S (A8) on sucrose density gradients. The enzyme from N. japonica contained more A8 than A12, while that of T. californica contained more A12. After treatment with collagenase, the enzymes gave three peaks on sedimentation; 20 S, 16 S and 11 S for N. japonica, and 19 S, 15 S and 11 S for T. californica, indicating the presence of collagen-like tails. On polyacrylamide gel electrophoresis in sodium dodecyl sulfate, the asymmetric acetylcholinesterase from N. japonica gave bands of Mr 140 000, 100 000, 70 000 and 60 000, while that from T. californica gave bands of Mr 140 000, 100 000, 70 000 and 55 000. The bands of Mr 70 000 and 140 000 were monomers and non-reducible dimers, respectively, of the catalytic subunits. The bands of Mr 60 000 and 55 000 were the tail subunits, since collagenase treatment of the purified enzymes markedly decreased the amounts of these components. The Mr 100 000 subunit constituted less than 3% of the total asymmetric acetylcholinesterase from N. japonica but 18% of that from T. californica. The tail subunits constituted 6-8% of the two preparations. The catalytic subunits and the Mr 100 000 subunits bound concanavalin A, indicating that they are glycoproteins. The amino acid compositions of the enzymes from N. japonica and T. californica were very similar. Both contained hydroxyproline and hydroxylysine, characteristic of the collagen-like tails. The enzyme required divalent metal ions for activity, but only Mn2+, Mg2+ and Ca2+ were effective. Mn2+ was effective at the lowest concentrations, while Mg2+ gave the highest activity.
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PMID:Comparison of asymmetric forms of acetylcholinesterase from the electric organ of Narke japonica and Torpedo californica. 300 Jul 81

Anatoxin-a(s) [antx-a(s)] is produced by Anabaena flos-aquae clone NRC 525-17 and is different from anatoxin-a, a known depolarizing agent produced by A. flos-aquae NRC 44-1. Purification of antx-a(s) from lyophilized cells involved extraction with 1.0 M acetic acid: ethanol (80:20), column chromatography (Sephadex G-15 and CM-Sephadex C-25) and high performance liquid chromatography. Purified toxin has an LD50 (i.p., mouse) of approximately 50 micrograms/kg. Gross pharmacological tests of antx-a(s) on isolated chick biventer cervicis and frog rectus abdominis muscles showed no direct agonistic effect. Instead, antx-a(s) augments the acetylcholine response and antagonizes the actions of d-tubocurarine. Twitch potentiation and tetanic fade were observed on isolated rat phrenic nerve--diaphragm muscle when stimulated indirectly at different frequencies. In acute toxicity tests with mice and rats the signs of poisoning were indicative of excessive cholinergic stimulation. Mice pretreated with atropine sulfate showed longer survival times and no parasympathomimetic signs of toxicity. The mice still died of respiratory arrest with convulsions, which indicated that toxicity is due to more than just the peripheral muscarinic action of antx-a(s). Assays of serum cholinesterase of rats in acute toxicity tests showed complete inactivation of the enzyme at doses of 350 and 600 micrograms/kg. It was concluded that antx-a(s) may be acting as an anticholinesterase, thereby causing toxicity.
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PMID:The pharmacology of anatoxin-a(s), a neurotoxin produced by the freshwater cyanobacterium Anabaena flos-aquae NRC 525-17. 308 30

The purification and characterization of acetylcholinesterase from heads of the fruit fly Drosophila are described. Sequential extraction procedures indicated that approximately 40% of the activity was soluble and 60% membrane-bound and that virtually none (less than 4%) corresponded to collagen-tailed forms. The membrane-bound enzyme was extracted with Triton X-100 and purified over 4000-fold by affinity chromatography on acridinium resin. Hydrodynamic analysis by both sucrose gradient centrifugation and chromatography on Sepharose CL-4B revealed an Mr of 165,000 similar to that observed for dimeric (G2) forms of the enzyme in mammalian tissues. In contrast, the purified enzyme gave predominant bands of about 100 kDa prior to disulfied reduction and 55 kDa after reduction on polyacrylamide gel electrophoresis in sodium dodecyl sulfate, values that are significantly lower than those reported for purified G2 enzymes from other species. However, the presence of a faint band at 70 kDa which could be labeled by [3H]diisopropyl fluorophosphate prior to denaturation suggested that the 55-kDa band as well as a 16-kDa species arose from proteolysis. This was confirmed by reductive radiomethylation and amine analysis of the 70-, 55-, and 16-kDa bands. All three contained ethanolamine and glucosamine residues that are characteristic of a C-terminal glycolipid anchor in other G2 acetylcholinesterases. The catalytic properties of the enzyme were examined by titration with a fluorogenic reagent which revealed a turnover number for acetylthiocholine that was 6-fold lower than eel and 3-fold lower than human erythrocyte acetylcholinesterase. Furthermore, the Drosophila enzyme hydrolyzed butyrylthiocholine much more efficiently than these eel or human enzymes, an indication that the fly head enzyme has a substrate specificity intermediate between mammalian acetylcholinesterases and butyrylcholinesterases.
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PMID:Isolation and characterization of acetylcholinesterase from Drosophila. 311 78


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