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 in vitro action of thyrotropin-releasing hormone (TRH) on the cyclic AMP level and iodine metabolism in dog thyroid, has been studied. TRH inhibited cyclic AMP accumulation and subsequent secretion in slices stimulated by thyrotropic hormone (TSH), prostaglandin E1, cholera toxin and to a lesser extent forskolin. The effect of TRH was suppressed in a medium deprived of calcium or in the presence of isobutylmethylxanthine. TRH also stimulated iodide binding to proteins, but not cyclic GMP accumulation. Although all these characteristics of TRH action on dog thyroid fit those of prostaglandin F1 alpha in this tissue, TRH effects were not relieved by indomethacine. The possibility of a TRH action through other known inhibitors of the cyclic AMP system in dog thyroid such as: acetylcholine, alpha-adrenergic agents, adenosine, iodide were checked and ruled out. The possible involvement of other neurotransmitters, such as ATP or vasoactive intestinal peptide were studied but could not be substantiated. Our data suggest the existence of a direct negative action of TRH on the thyroid itself besides its stimulatory role at the pituitary level. The great variability of the TRH effect was overcome by pretreatment of the dog by pyridostigmine, an acetylcholinesterase inhibitor.
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PMID:Effect of thyrotropin-releasing hormone on dog thyroid in vitro. 619 95

The effects of oleic acid (oleate) were examined using two in vitro model systems. In a concentration-dependent fashion oleate activated or inhibited the (Ca2+ + Mg2+)-ATPase, or Ca2+ pump ATPase, of membranes isolated from human red blood cells (RBC's). Concentrations of oleate which inhibited the Ca2+ pump ATPase also inhibited the Na+-K+ pump ATPase. Likewise, in a concentration-dependent fashion oleate increased or abolished ATP dependent 45Ca2+ transport into inside-out vesicles (IOV's) prepared from human RBC's. Addition of 500 microM oleate to IOV's which had already accumulated 45Ca2+ resulted in rapid loss of the ion. The effect was shown to be due to membrane disruption; a conclusion based on oleate-induced unmasking of latent acetylcholinesterase activity in IOV preparations. The results are compatible with, but do not prove, that membrane disruption caused by circulating free fatty acids and similar membrane active agents might play a role in the cellular injury associated with certain pathophysiologic states.
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PMID:Apparent inhibition of the plasma membrane Ca2+ pump by oleic acid. 622 99

The activity of Na+, K+ATPase (EC 3.6.1.3) and acetylcholinesterase (EC 3.1.1.7) as well as the content of masked and exposed SH-groups in sealed and unsealed erythrocyte ghosts were studied as affected by single rapid freezing-thawing. The freezing-thawing procedure resulted in different reactions of membrane-bound enzymes: Na+, K+-ATPase activity is doubled in sealed ghosts and unchanged in unsealed ones. In both types of ghosts the equal decrease in the AChE activity was found to be parallel with the diminution in the content of masked SH-groups but this cannot be referred to exposed SH-groups. The obtained results seem to suggest that the changes in the native conformation of membrane catalytic proteins resulted from cryodamage are responsible for the lowered aChE activity; the primary cause of increase Na+, K+-ATPase activity is due to the changes in the permeability and integrity of erythrocyte membrane, which are followed by the greater accessibility of the substrate (ATP) to the enzyme.
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PMID:[Changes in Na+, K+-ATPase and acetylcholinesterase activity in red cell membranes after freezing-thawing]. 626 9

A method has been developed for the isolation of sealed plasma membrane vesicles from rabbit white skeletal muscle. The final preparation was highly purified as indicated by enrichment of plasma membrane marker enzymes (i.e. ouabain-sensitive (Na+,K+)-ATPase, adenylate cyclase, and acetylcholinesterase). The absence of sarcoplasmic reticulum and mitochondria as contaminants was indicated by the low specific activity of marker enzymes, i.e. Ca2+-ATPase, succinate-cytochrome c reductase, and monoamine oxidase. Thin section and negative staining electron microscopy confirmed the absence of sarcoplasmic reticulum and mitochondrial contamination. The plasma membrane preparation consisted largely of sealed vesicles as observed by electron microscopy and as also demonstrated by latency of enzymic activities, which were unmasked by preincubation with detergent (sodium dodecyl sulfate). Membrane sidedness was estimated from latency of ouabain-sensitive (Na+,K+)-ATPase activity and acetylcholinesterase activity. The latency studies suggest that most of the vesicles are oriented inside out with respect to the orientation of the sarcolemma membrane in the muscle fiber. The inside-out plasma membrane vesicles actively accumulated sodium ions upon addition of ATP. The sodium ions were concentrated greater than 8-fold inside the vesicles and were released upon addition of the ionophore monensin. The sodium ions were taken up in the presence of K+ or NH4+ but not of choline. Uptake was inhibited by low concentrations of vanadate or digitoxin. The Na+ uptake was concomitant with Rb+ efflux. Therefore, the sodium ion transport and the resulting gradients formed appear to have been generated by the ouabain-sensitive (Na+,K+)-ATPase. Batrachotoxin, which opens Na+ channels in excitable tissues, prevents most of the Na+ uptake, suggesting the presence of toxin-activated Na+ channels in these plasma membrane vesicles.
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PMID:Isolation of plasma membrane vesicles from rabbit skeletal muscle and their use in ion transport studies. 629 11

The activity of pyruvate dehydrogenase phosphate (PDHb) phosphatase in rat brain mitochondria and homogenate was determined by measuring the rate of activation of purified, phosphorylated (i.e., inactive) pyruvate dehydrogenase complex (PDHC), which had been purified from bovine kidney and inactivated by phosphorylation with Mg . ATP. The PDHb phosphatase activity in purified mitochondria showed saturable kinetics with respect to its substrate, the phospho-PDHC. It had a pH optimum between 7.0 and 7.4, depended on Mg and Ca, and was inhibited by NaF and K-phosphate. These properties are consistent with those of the highly purified enzyme from beef heart. On subcellular fractionation, PDHb phosphatase copurified with mitochondrial marker enzymes (fumarase and PDHC) and separated from a cytosolic marker enzyme (lactate dehydrogenase) and a membrane marker enzyme (acetylcholinesterase), suggesting that it, like its substrate, is located in mitochondria. PDHb phosphatase had similar kinetic properties in purified mitochondria and in homogenate: dependence on Mg and Ca, independence of dichloroacetate, and inhibition by NaF and K-phosphate. These results are consistent with there being only one type of PDHb phosphatase in rat brain preparations. They support the validity of the measurements of the activity of this enzyme in brain homogenates.
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PMID:Pyruvate dehydrogenase phosphate (PDHb) phosphatase in brain: activity, properties, and subcellular localization. 630 Mar 32

Several dibenzazepines, thioxanthene, and phenothiazine stereoisomers were studied for their abilities to inhibit plasmid replication, intracellular transfer of R-plasmid, bacterial ATP-ase, and mouse serum cholinesterase isoenzyme. Partially saturated derivative of desipramine inhibited plasmid replication and transfer, but the fully saturated derivative was inactive. The inhibition of plasmid curing and transfer patterns did not correlate with the inhibition of ATP-ase and cholinesterase. Trans-clopenthixol was more effective in plasmid elimination than the cis-isomer. On the other hand, the cis-isomer inhibited ATP-ase and cholinesterase more than the trans-isomer. The levo- and dextro-methoxytrimeprazine also inhibited plasmid replication and enzyme activity. We believe that the tricyclic configuration of the drugs tested for stereospecific binding to bacterial receptors is more important than its side chain orientation. We believe that there is a similarity between bacterial receptor sites and neural receptor sites. Therefore, this model may be useful in the study of neuropharmacological agents as potential antibacterial agents.
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PMID:Inhibition of bacterial plasmid replication by stereoselective binding by tricyclic psychopharmacons. 636 55

1. An inhibitor of erythrocyte membrane (Ca2+ + Mg+)-ATPase was isolated from membrane-free pig haemolysate through treatment with diethylaminoethyl-Sephacel and carboxymethyl-Sephadex at pH 6.8. The resulting inhibitor preparation was devoid of (Ca2+ + Mg2+)-ATPase activator protein. 2. The inhibitor was without effect on erythrocyte membrane acetylcholinesterase, ouabain-sensitive ATPase and spectrin (Ca2+ + Mg2+)-ATPase. 3. The inhibitor was active in suppressing activator sensitive, ATP-dependent calcium transport across erythrocyte membrane.
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PMID:An endogenous inhibitor of erythrocyte membrane (Ca2+ + Mg2+)-ATPase involved in calcium transport. 644 1

Storage of human erythrocytes in SAG media results in the release of membrane microvesicles with a diameter of about 190 nm. They can be separated from intact erythrocytes by centrifugation on a dextran barrier solution (density 1.078 g/l). Vesicles prepared from cold stored erythrocyte concentrates are like those released upon ATP depletion by erythrocytes incubated without glucose at 37 degrees C [15]. The course of vesiculation was followed by measuring acetylcholinesterase during storage of the erythrocyte concentrate for 35 days. Its activity remained constant within the storage units during the preservation period. This enzyme and phospholipids were released continuously in a proportional manner. The release of sialic acid amounted to about half of that of phospholipids. Owing to depletion of 2,3-bisphosphoglycerate the binding of ATP to haemoglobin increased and the concentration of free ATP declined. Addition of an ion-exchange resin to stored erythrocytes kept the pH constant, retarded the breakdown of 2,3-P2G and stabilized the concentration of free ATP. That inhibited the rate of irreversible vesiculation. Therefore, maintenance of 2,3-bisphosphoglycerate plus ATP during long-term storage of erythrocytes is a condition of keeping intact their membrane, metabolism and oxygen transport function.
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PMID:Release of microvesicles from erythrocytes during storage in saline-adenine-glucose media. 653 40

An assay capable of detecting tens-of-picomole quantities of choline and acetylcholine in milliliter volumes of a physiological salt solution has been developed. Silica column chromatography was used to bind and separate 10-3000 pmol [14C]choline and [14C]acetylcholine standards made up in 3 ml of a bicarbonate-buffered Krebs-Ringer solution. The silica columns bound 95-98% of both choline and acetylcholine. Of the bound choline 84-87% was eluted in 1.5 ml of 0.075 N HCl, whereas 95-98% of the bound acetylcholine was eluted in a subsequent wash with 1.5 ml of 0.030 N HCl in 10% 2-butanone. Vacuum centrifugation of the eluants yielded small white pellets with losses of choline and acetylcholine of only 1%. Dried pellets of unlabeled choline and acetylcholine standards were assayed radioenzymatically using [gamma-32P]ATP, choline kinase, and acetylcholinesterase. The net disintegrations per minute of choline[32P]phosphate product was proportional to both the acetylcholine (10-3000 pmol) and choline (30-3000 pmol) standards. The "limit sensitivity" was 8.5 pmol for acetylcholine and 11.4 pmol for choline. Cross-contamination of the choline assay by acetylcholine averaged 1.3%, whereas contamination of the acetylcholine assay by choline averaged 3.1%.
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PMID:Determination of picomole quantities of acetylcholine and choline in physiologic salt solutions. 673 54

We adapted a method, originally described by Israel et al. (1976) for the preparation of cholinergic nerve endings from Torpedo, to deal with a larger quantity of electric tissue. We followed the distribution of acetylcholine (ACh), ATP, acetylcholine receptor (AChR), choline acetyltransferase (ChAT), ouabain-resistant and -sensitive ATPase, lactate dehydrogenase (LDH), and acetylcholinesterase (AChE), and obtained a nerve ending fraction, without detectable contamination by postsynaptic components. This preparation consisted of closed structures of 1-5 micrometers diameter, containing synaptic vesicles. It had the capacity to synthetize and release ACh. This preparation is therefore quite suitable for biochemical analysis of presynaptic elements. We particularly investigated its content of AChE: it consists exclusively of the 6S dimeric, hydrophobic form of the enzyme. This enzyme is enriched in the nerve ending preparation, by a factor higher than that obtained for ChAT. The yields obtained for the two enzymes suggest that the hydrophobic 6S AChE form may be mostly presynaptic in Torpedo electric organs. We characterized this form as a membrane-bound, externally active enzyme in the nerve ending preparation. It may thus participate in the hydrolysis of extracellularly liberated AChE, and its abundance suggests that presynaptic AChE could play an essential role in cholinergic transmission in Torpedo electric organs and perhaps also in other cholinergic synapses.
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PMID:Presence of a membrane-bound acetylcholinesterase form in a preparation of nerve endings from Torpedo marmorata electric organ. 682 28


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