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)

Lipoprotein forms of acetylcholinesterase from bovine erythrocytes gave non-linear Arrhenius plots with a break at 20 degrees C and contained cardiolipin. The break in the Arrhenius plot was abolished by incubation of the enzyme in high salt (I = 1.8), but only in Ca2+ -chelating conditions. At I = 1.8 neither NaCl alone, CaCl2 nor sodium phosphate at acidic pH abolished the break. However, at this ionic strength either NaCl in 2 mM sodium phosphate (pH 7.4) or sodium phosphate, pH 8, or 1.0 M Na2CO3/NaHCO3 (pH 8.5--10, were able to remove the break. The Arrhenius plot break was regenerated by the addition of Ca2+ to the high salt-treated enzyme with mild homogenization, but could not be regenerated in the presence of EDTA unless CaCl2 was added in excess of the EDTA. Conditions which abolished the break enabled endogenous cardiolipin to be removed from the enzyme by chloroform/methanol extraction Cardiolipin from acetylcholinesterase incubated in high salt in Ca2+ -chelating conditions was not accessible to digestion by phospholipase A2, and was not separated from the enzyme by flotation in a sucrose density gradient or by Sephadex G-200 chromatography. Thus both Ca2+ and cardiolipin appear to be inaccessible, possibly by being tightly associated in the hydrophobic core of the enzyme by ionic and hydrophobic forces. Ca2+ may modulate the temperature dependence of acetylcholinesterase activity through a functionally linked ionic interaction with the enzyme-cardiolipin complex.
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PMID:Involvement of calcium ions in the properties of cardiolipin-associated erythrocyte acetylcholinesterase. 54 28

A procedure is described for the isolation of synaptic membrane fragments that retain such functionally important proteins as acetylcholine receptors, acetylcholinesterase, 3',5'-cyclic nucleotide phosphodiesterase, and (Na+ + K+)-ATPase. The method is based on the observation, made in brain slices, that junctional membranes are more resistant to phospholipase A2 attack than mitochondrial or plasma membranes. Hydrolysis by phospholipase A2 was controlled by addition of fatty acid-free bovine serum albumin. The membrane fraction obtained represents approximately a 15-fold enrichment of the postsynaptic marker proteins muscarinic and nicotinic acetylcholine receptor and 3',5'-cyclic nucleotide phosphodiesterase over an ordinary synaptic plasma membrane preparation, and is devoid of mitochondrial and microsomal contaminations. The membranes appear on the electron micrographs as rigid fragments (average length 2500-4000A), which do not form vesicles.
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PMID:Isolation of a synaptic membrane fraction enriched in cholinergic receptors by controlled phospholipase A2 hydrolysis of synaptic membranes. 125 6

A protein fatty acylesterase activity that catalyzes the removal of fatty acid from exogenous proteolipid protein (PLP) has been demonstrated in isolated rat brain myelin. Optimum enzyme activity for the deacylation of PLP was obtained in 0.5% Triton X-100, 1 mM dithiothreitol at pH 7.0 and at 37 degrees C. Other detergents (octyl beta-D-glucoside, Nonidet P-40, and Tween 20) have little or no effect, whereas deacylation was completely abolished by 0.1% sodium dodecyl sulfate or boiling the membrane fraction for 5 min prior to incubation. Under optimal conditions, the rate of deacylation was linear up to 20 min, and the apparent Km for bovine [3H]palmitoyl-PLP was 18 microM. The myelin-associated PLP fatty acylesterase has no apparent requirements for divalent cations (Ca2+, Mg2+, Mn2+), and chelators such as EDTA, [ethylenebis(oxyethylenenitrilo)] tetraacetic acid, and 1,10-phenantroline have little or no effect on enzyme activity. Sulfhydryl and histidine residues are needed for full enzyme activity, whereas the "active serine"-directed inhibitor phenylmethylsulfonyl fluoride has no effect. The myelin-associated protein fatty acylesterase was present throughout brain development and in all myelin subfractions, in agreement with the dynamic metabolism of PLP-bound fatty acids. Enzyme activity was also present in sciatic nerve, brain cortex, and heart whereas liver was devoid of activity. Several esterases, including phospholipase A2, glyoxalase II, and acetylcholinesterase, did not remove fatty acid from PLP. Myelin basic protein, palmitoyl-CoA hydrolase, and myelin-associated nonspecific esterase were also ruled out as the PLP fatty acylesterase. Thus, all data seem to indicate that this enzyme is different from esterases of the lipid metabolism. Finally, stimulation of protein phosphorylation with Ca2+, but not with cyclic-AMP, inhibited PLP deacylation, suggesting that the myelin-associated protein fatty acylesterase activity is regulated by endogenous Ca(2+)-dependent protein kinases.
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PMID:Characterization of proteolipid protein fatty acylesterase from rat brain myelin. 156 18

Several proteins including bovine erythrocyte acetylcholinesterase are anchored in the membrane through glycoinositol phospholipids containing an alkyl linkage at the sn-1 position of the glycerol. However, the existence of 1-alkyl-2-acyl-sn-glycero-3-phosphoinositol (alkylacyl-GPI) in biological systems has not been demonstrated. In this study, we identified the presence of alkylacyl-GPI in bovine erythrocytes by the following criteria: (1) TLC-Rf value, (2) radyllyso-GPI was produced after phospholipase A2 treatment of the diradyl-GPI, and (3) benzoate derivatives of alkylacylglycerols produced by phospholipase C hydrolysis of diradyl-GPI had the same retention time as that of authentic alkylacylglycerobenzoates on normal-phase HPLC. Diradyl-GPI consisted of 5-10% alkylacyl-GPI. Reverse-phase HPLC analysis of alkylacylglycerobenzoates derived from bovine erythrocyte alkylacyl-GPI showed a multiplicity of species with 18:0-20:4 (11.7%), 16:0-18:1 + 18:0-18:2 (34.9%), and 18:0-18:1 (19.4%) being the major components. Composition of alkyl chains of alkylacyl-GPI from bovine erythrocytes was similar to the reported value for alkylacylglycerols isolated from the glycoinositol phospholipid anchor of bovine erythrocyte acetylcholinesterase. Based on these results, we suggest that alkylacyl-GPI serves as a precursor for the glycoinositol phospholipid of the anchored proteins.
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PMID:Occurrence of ether-containing inositol phospholipids in bovine erythrocytes. 182 38

The resting efflux of choline into the perfusate (Tyrode's solution) of isolated hearts was equal to the rate, at which choline was liberated from phospholipid degradation (Lindmar et al. 1986). Infusion of isoprenaline (2 X 10(-7) mol/l), forskolin (1-3 X 10(-6) mol/l) or 3-isobutyl-1-methylxanthine (IBMX; 3 X 10(-4) mol/l) for 40 min markedly enhanced the efflux of choline. The increase was linear during the experimental period and, in the case of isoprenaline, was blocked by 3 X 10(-7) mol/l atenolol. In the guinea-pig heart, IBMX at a threshold concentration of 10(-4) mol/l shifted the concentration-response curve for the effect of forskolin on the efflux of choline to the left by one log unit. Forskolin (10(-6) mol/l) increased also the tissue content of cyclic AMP. This effect and the increase of choline efflux evoked by forskolin were blocked by 2 X 10(-7) mol/l carbachol. Likewise, inhibition of cholinesterase activity caused by diisopropylfluorophosphate antagonized the forskolin-evoked acceleration of choline efflux indicating a response to endogenous acetylcholine. The muscarinic inhibition of the enhanced choline efflux was reversed by 3 X 10(-7) mol/l atropine. The phospholipase A2 inhibitor mepacrine as well as infusion of a low Ca2+-Tyrode's solution (0.2 instead of 1.8 mmol/l) blocked the effect of forskolin on choline efflux, whereas the generation of cyclic AMP by forskolin was unaffected by low Ca2+-solution.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The release of choline from phospholipids mediated by beta-adrenoceptor activation in isolated hearts. 243 3

When human erythrocytes are treated with Staphylococcus aureus sphingomyelinase C at 37 degrees C they become susceptible to cold lysis and appear to endovesiculate. Endovesiculation has been confirmed by showing that in parallel with sphingomyelin breakdown, the cells accumulate [3H]inulin or [14C]sucrose (without losing intracellular K+) and also experience a loss of cell-surface acetylcholinesterase activity into a latent intracellular pool which can be revealed by treatment with detergent. On the basis of these observations it can be calculated that endovesicles account for about 2-4% of cell volume and about 25% of total cell surface. Pretreatment of cells with bee venom phospholipase A2 completely blocked sphingomyelinase-induced endovesiculation but this effect was related to a concomitant decrease in sphingomyelin breakdown which was reduced by about 90%. These results indicate that the pool of sphingomyelin which is not susceptible to attack by sphingomyelinase C (about 15% of total sphingomyelin) may be resistant because of membrane internalisation and not because it originally resides in the inner leaflet of the plasma membrane.
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PMID:Endovesiculation of human erythrocytes exposed to sphingomyelinase C: a possible explanation for the enzyme-resistant pool of sphingomyelin. 283 79

The proposed system of continuous monitoring of enzyme activities is based primarily on the electrochemical behaviour of thiol compounds, and the experimental equipment is extremely simple. The determination of cholinesterase (EC 3.1.1.8) activity is described. The normal values obtained for men (73.9, s +/- 10.3 microkat/l) and for women (71.1, s +/- 10.2 microkat/l), lie within the usual range of analogous photometric methods. Systems for determination of the activities of alkaline phosphatase (EC 3.1.3.1) and adenosylhomocysteinase (EC 3.3.1.1) are described. The activity of aspartate aminotransferase (EC 2.6.1.1) is determined by a combination of enzyme reactions, in which CoA is released from acetyl-CoA. Analogous procedures are discussed for determinations of alanine aminotransferase (EC 2.6.1.2), lactate dehydrogenase (EC 1.1.1.27), lipase (EC 3.1.1.2), and phospholipase A2 (EC 3.1.1.4) activities, and for determination of substrates, e.g., acetate and carnitine. Possible determinations of an additional 199 enzyme activities and of some of substrates are suggested. By determining electrochemically active groups other than thiols this method becomes almost universally applicable.
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PMID:New system of continuous monitoring of enzyme activities and determination of some substrates. 344 Aug 58

The resting efflux of choline from perfused chicken hearts varied from 0.4 to 2.6 nmol/g min, but was constant for at least 80 min in the individual experiments. The rate of choline efflux was found to be equal to the rate of choline formation in the heart, which, from the following reasons, was essentially due to hydrolysis of choline phospholipids. Cardiac content of choline phospholipids (7,200 nmol/g) was much higher than that of acetylcholine (5.5 nmol/g). Resting release of acetylcholine was 0.016 nmol/g min and, after inhibition of cholinesterase, only about 0.1 nmol/g min. Resting efflux of choline was reduced by mepacrine, a phospholipase A2 inhibitor, by perfusion with a Ca2+-free Tyrode's solution containing EGTA and by the combination mepacrine plus Ca2+-free/EGTA solution. In all experiments the reduced choline efflux levelled off within 10 min at about 50%. Omission or elevation of Mg2+ from 1.05 to 10.5 mmol/l had no effect. Resting efflux was increased to 150% by oleic acid (as sodium salt; 2 X 10(-5) mol/l) which is known to activate phospholipase D. Likewise muscarinic agonists (carbachol and acetylcholine) caused facilitation of the efflux of endogenous choline that was blocked by 3 X 10(-7) mol/l atropine. This effect was not reduced, but even slightly enhanced, by mepacrine and by infusion of EGTA in a modified Tyrode's solution (Ca2+-free, 10.5 mmol/l Mg2+). It is concluded that the resting efflux of choline from the heart is essentially due to hydrolysis of choline phospholipids, that half of the efflux is insensitive to mepacrine and is Ca2+-independent (excluding an involvement of phospholipase A2).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of choline efflux from the perfused heart at rest and after muscarine receptor activation. 371 69

By measuring the permeability across the lipid bilayer in the presence and absence of membrane-bound protein or glycoprotein it should be possible to get an impression concerning their ability to penetrate into the membrane bilayer. Proteins such as phospholipase A2 and acetylcholinesterase markedly increase the permeability in contrast to glycoproteins (ovomucoid and orosomucoid) and cytochrome C. The results may serve as an indication of the type of interaction between lipids and membrane components.
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PMID:Glycoprotein and protein induced changes in liposome permeability. 628 80

Human erythrocytes were treated with various hydrophobic arylisothiocyanates under conditions which favor modification of distinct proteinaceous nucleophiles. The morphological appearance of phenylisothiocyanate-treated cells was discoid and membrane-bound hydrolases (human acetylcholinesterase, sheep phospholipase A2) were fully active following membrane modification. Noncharged hydrophobic arylisothiocyanates, including phenylisothiocyanate, beta-naphthylisothiocyanate and heterobifunctional azidoarylisothiocyanates inhibited [35S]-sulfate efflux irreversibly. Protection against modification-induced inhibition of sulfate transport was attained by the simultaneous presence of the specific reversible anion transport inhibitor 4,4'-dinitrostilbene-2,2'-disulfonate. Selective protection of a functionally relevant domain of band 3 is concluded to occur based on the above-derived information.
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PMID:Functional evidence for distinct interaction of hydrophobic arylisothiocyanates with the erythrocyte anion transport protein. 649 34


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