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)

The type of membrane association of acetylcholinesterase (AChE, EC 3.1.1.7) was studied in rabbit lymphocytes and erythrocytes. In both cases, the unique AChE molecular form was an amphiphilic dimer (referred to as G2a) anchored in the membrane by a glycosylphosphatidylinositol. In lymphocytes, G2a AChE was directly converted into its hydrophilic G2h counterpart by a treatment with Bacillus thuringiensis phosphatidylinositol-phospholipase C (PI-PLC, EC 3.1.4.10). In erythrocytes, AChE was resistant to PI-PLC but was rendered sensitive by a prior deacylation with alkaline hydroxylamine. This observation suggests that, as previously reported for human erythrocyte AChE, an acylation of the inositol ring in the glycolipid anchor of rabbit erythrocyte AChE (that does not occur in lymphocytes) prevents the cleavage.
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PMID:Glycolipid-anchored acetylcholinesterases from rabbit lymphocytes and erythrocytes differ in their sensitivity to phosphatidylinositol-specific phospholipase C. 132 66

To obtain information about the mode of attachment of amphiphilic monomers of acetylcholinesterase (AChE) in sarcoplasmic reticulum (SR) of skeletal muscle, attempts were made to release the enzyme by alkaline hydroxylamine. About half of the activity measured in microsomes preincubated with 0.5% (w/v) Triton X-100 is detached by incubation of SR with bicarbonate buffer (pH 10.5). Addition of 1 M hydroxylamine to the alkaline buffer did not improve enzyme solubilization. Molecular forms of 16S (A12), 10.5S (G4) and 4.0S (G1) are separated by sedimentation analyses of Triton X-100 or bicarbonate-solubilized AChE. Monomeric AChE, released under alkaline conditions (G1A), displays amphiphilic properties. G1A, but not G4 and A12, forms are retained in a phenyl-Sepharose column and this allows its separation from hydrophilic forms. Isolated monomers extracted with Triton X-100 (G1D) or alkaline buffer showed identical kinetic behaviour. The two forms reacted with lectins in a similar manner. However, thermal inactivation experiments revealed that about 90 and 40% of the activity in the G1D and G1A forms were lost by heating at 50 degrees C, following the same rate constant (k = 0.130 min-1). Addition of Triton X-100 to the G1A form leads to an increase of its thermal sensitivity, the enzyme being fully inactivated very rapidly (k = 0.230 min-1). The results suggest that the hydrophobic moiety of the enzyme might be exposed or hidden depending on the environmental hydrophobicity. Changes in the composition of the solvent will determine the final conformational state of the protein.
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PMID:Alkaline treatment of muscle microsomes releases amphiphilic and hydrophilic forms of acetylcholinesterase. 159 55

The anticancer drug caracemide, N-acetyl-N,O- di(methylcarbamoyl)hydroxylamine, and one of its degradation products, N-acetyl-O-methylcarbamoyl-hydroxylamine, were found to inhibit the enzyme ribonucleotide reductase of Escherichia coli by specific interaction with its larger component protein R1. No effect on the smaller protein R2 was observed. The effect of the degradation product was about 30 times lower than that of caracemide itself. The caracemide inactivation of R1 is irreversible, with an apparent second-order rate constant of 150 M-1 s-1. The R1R2 holoenzyme was approximately 30 times more sensitive to caracemide inactivation than the isolated R1 protein. The ribonucleotide reductase substrates were potent competitors of the caracemide inhibition, with a Kdiss for GDP binding to R1 of 80 microM. The reducing agent dithiothreitol was also found to be a potent competitor of caracemide inactivation. These results indicate that caracemide inactivates R1 by covalent modification at the substrate-binding site. By analogy with the known interaction between caracemide and acetylcholinesterase or choline acetyltransferase, we propose that the modification of R1 occurs at an activated cysteine or serine residue in the active site of the enzyme.
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PMID:Caracemide, a site-specific irreversible inhibitor of protein R1 of Escherichia coli ribonucleotide reductase. 161 68

1. We describe two simple procedures for the rapid identification of certain structural features of glycolipid anchors in acetylcholinesterases (AChEs). 2. Treatment with alkaline hydroxylamine (that cleaves ester-linked acyl chains but not ether-linked alkyl chains) converts molecules possessing a diacylglycerol, but not those with an alkylacylglycerol, into hydrophilic derivatives. AChEs in human and bovine erythrocytes possess an alkylacylglycerol (Roberts et al., J. Biol. Chem. 263:18766-18775, 1988; Biochem. Biophys. Res. Commun. 150:271-277, 1988) and are not converted to hydrophilic dimers by alkaline hydroxylamine. Amphiphilic dimers of AChE from Drosophila, from mouse erythrocytes, and from the human erythroleukaemia cell line K562 also resist the treatment with hydroxylamine and likely possess a terminal alkylacylglycerol. This indicates that the cellular pool of free glycolipids used as precursors of protein anchors is distinct from the pool of membrane phosphatidylinositols (which contain diacylglycerols). 3. Pretreatment with alkaline hydroxylamine is required to render the amphiphilic AChE from human erythrocytes susceptible to digestion by Bacillus thuringiensis phosphatidylinositol-specific phospholipase C (PI-PLC) (Toutant et al., Eur. J. Biochem. 180:503-508, 1989). We show here that this is also the case for the AChE from mouse erythrocytes, which therefore likely possesses an additional acyl chain in the anchor that prevents the action of PI-PLC. 4. In two sublines of K562 cells (48 and 243), we observed that AChE either was directly susceptible to PI-PLC (243) or required a prior deacylation by alkaline hydroxylamine (48). This suggests that glycolipid anchors in AChE of K562-48 cells, but not those in AChE of K562-243 cells, contain the additional acylation demonstrated in AChE from human erythrocytes. These observations illustrate the cell specificity (and the lack of species-specificity) of the structure of glycolipid anchors.
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PMID:Rapid analysis of glycolipid anchors in amphiphilic dimers of acetylcholinesterases. 184 55

Each catalytic subunit in the amphiphilic dimer of human erythrocyte acetylcholinesterase (AChE) is anchored in the plasma membrane exclusively by a glycoinositol phospholipid. In contrast to erythrocyte AChEs in other mammalian species, the human enzyme is resistant to direct cleavage by phosphatidylinositol-specific phospholipase C (PtdIns-specific PLC). The resistance is due to the existence of an additional fatty acyl chain on the inositol ring which blocks the action of PtdIns-specific PLC [Roberts et al. (1988) J. Biol. Chem. 263, 18766-18775]. In this report, nondenaturing polyacrylamide gel electrophoresis was applied to permit rapid and unambiguous distinction between amphiphilic AChE, in which each catalytic subunit binds one nonionic detergent micelle, and hydrophilic AChE, which does not interact with detergent. Deacylation of human erythrocyte AChE by an alkaline treatment with hydroxylamine rendered the amphiphilic AChE susceptible to PtdIns-specific PLC with the consequent release of hydrophilic AChE. Although serum anchor-specific phospholipase D (PLD) cleaves the intact human erythrocyte AChE anchor, this treatment, as judged by nondenaturing electrophoresis, did not release hydrophilic AChE. Hydroxylamine treatment before or after PLD digestion was necessary to achieve the conversion. These observations indicate that binding of a single detergent micelle was maintained when any of the three fatty acyl or alkyl groups in the human erythrocyte AChE anchor phospholipid were retained. For proteins that can be identified following nondenaturing gel electrophoresis, these procedures provide methods both for detecting glycoinositol phospholipid anchors resistant to PtdIns-specific PLC and for indicating fatty acyl and/or alkyl chains in these anchors.
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PMID:Conversion of human erythrocyte acetylcholinesterase from an amphiphilic to a hydrophilic form by phosphatidylinositol-specific phospholipase C and serum phospholipase D. 254 Sep 62

Human plasma cholinesterase was found to be inhibited by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide in a biphasic manner. The faster phase of the inhibition led to loss of approximately 50% of the activity (measured at pH 7.0, 30 degrees C, using 2.5 mM butyrylthiocholine) and was irreversible. Inhibition in the slower phase was reversible by 0.25 M hydroxylamine. The protective effect of 1 mM propranolol indicated that the target residue in both phases was localized at the active site. Lineweaver-Burk plots for butyrylthiocholine were obtained at different times during the course of inactivation. It was found that for both native and partially inactivated enzymes the plots could be analyzed in terms of two activities showing hyperbolic saturation with the substrate, with Km values of 0.055 +/- 0.015 and 2.0 +/- 0.2 mM. The carbodiimide affected the maximal velocities of the component activities, leaving the Km's unchanged. The low-Km component was lost in the first phase of the inactivation. The loss of the high-Km component paralleled the second phase. It was concluded that the active sites in the tetrameric enzyme form two classes, differing in their affinity for butyrylthiocholine and their susceptibility to inhibition by the active site-directed carbodiimide.
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PMID:Differential reactivity of active sites in human plasma cholinesterase toward 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. 359 72

Hydroxylamine chloride (0.3 g/l) in drinking water was given to 3-mo-old male Wistar rats for 1 to 63 days. The treatment caused splenomegalia while no effect was noted on the weight gain. Cerebral RNA content was also unaffected whereas slight decrease in the cerebral homogenate and isolated glial cell succinate dehydrogenase activities was found. Creatine kinase activity in the glial cell fractions increased after 63 days. An initial increase in the muscle acetylcholinesterase activity resolved in muscle after 2 wks while increased muscle creatine kinase activity was found throughout the experiment. The splenomegalia might have been caused by methemoglobinemic red cell fragility, an established NH2OH effect, while the neurochemical effects and effects on muscle might have resulted from direct toxicity rather than from the relative hypoxia because of impaired oxygen transport capacity.
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PMID:Neurochemical effects of ingested hydroxylamine. 608 90

Commercial hexane was concentrated by distillation. The distillation residue (0.43 ml/l original solvent) contains material which inhibits human serum cholinesterase (ChE) "in vitro" with a slight effect on acetylcholinesterase. Phosphorus was detected equivalent to 0.33 mumol monophosphorus compound/litre original solvent. The inhibition was progressive with the enzyme-inhibitor preincubation time. A partial reactivation of the inhibited enzyme was obtained by treatment with hydroxylamine and 2-PAM. The results are coherent with a covalent inactivation by more than one inhibitor which acylate (probably phosphorylate) ChE, although it seems likely that a reversible but unstable inhibitor could also be present in the hexane residue. The results are discussed in the context of the known neurotoxic effects of n-hexane and some organophosphorus esters.
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PMID:Serum cholinesterase inhibitors in the commercial hexane impurities. 688 13

Amphiphilic monomers and dimers of acetylcholinesterase (AChE) and hydrophilic tetramers of butyrylcholinesterase (BuChE) were released by extracting human meningioma with Tris-saline and Tris-saline-Triton X-100 buffers. The amphiphilic or hydrophilic behavior of the AChE and BuChE forms was assessed by sedimentation analysis, hydrophobic chromatography and Triton X-114 phase-partitioning. A significant fraction of the amphiphilic AChE species was converted into hydrophilic components by incubation of the soluble enzyme with phosphatidylinositol-specific phospholipase C (PIPLC) from Bacillus thuringiensis, this fraction being increased by a double treatment with PIPLC and alkaline hydroxylamine. A significant amount of the membrane-bound AChE was released by incubation with PIPLC. These results demonstrate that AChE forms in meningioma are attached to the membrane via glycosylphosphatidylinositol, although part of the enzyme forms are resistant to PIPLC.
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PMID:Monomers and dimers of acetylcholinesterase in human meningioma are anchored to the membrane by glycosylphosphatidylinositol. 747 60

The principal initial degradation products of two bis(pyridinium)aldoxime organophosphate-inhibited acetylcholinesterase reactivators, 1 (HI-6) and 3 (HS-6), in concentrated nonbuffered aqueous solutions approximating potential therapeutic dosage concentrations were found to be the carboxylic acid derivatives 2 and 4 formed from the hydrolysis of the amide functional group. Compounds 2 and 4 were prepared by heating 1 and 3 in the presence of high concentrations of hydroxylamine hydrochloride and characterized by 1H and 13C NMR, IR, and UV analyses. Estimates of the rates of hydrolysis of the amide groups in 1 and 3 and in model compounds 5, 7, and 8 under similar conditions were determined. The unexpectedly rapid hydrolysis of the amide groups in 1 and 3 was attributed to both the hydrogen ion catalysis of the concentrated aqueous solutions of the unusually acidic bis(pyridinium)aldoximes 1 and 3 and general acid catalysis by the aldoxime group.
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PMID:Degradation of three related bis(pyridinium)aldoximes in aqueous solutions at high concentrations: examples of unexpectedly rapid amide group hydrolysis. 837 13


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