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:3.1.1.8 (cholinesterase)
12,691 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A single form of cholinesterase was detected in the parasitic nematode Parascaris equorum and purified from a low-salt Triton X-100 extract of whole animals by affinity chromatography on an edrophonium-Sepharose matrix. Based on gel-filtration chromatography, sedimentation analysis and SDS-PAGE, such a cholinesterase is an amphiphilic globular (G2) dimer (125-129 kDa, 6.1 S). It includes some hydrophobic domain other than phosphatidylinositol, which gives autoaggregation, detergent interaction and also anchors the molecule to the cell membrane. The enzyme, probably functional in cholinergic neurotransmission, is an acetylcholinesterase showing a fairly low substrate specificity with thiocholine esters. Electrostatic interactions seem to play a major role in the catalytic activity. Studies with inhibitors gave complete inhibition with 1 mM eserine, low sensitivity for procainamide and for tetra(monoisopropyl)pyrophosphortetramide as well as higher inhibition with edrophonium chloride and 1,5-bis(4allyldimethylammoniumphenyl)-pentan-3-one dibromide. The enzyme also showed excess-substrate inhibition with acetylthiocholine. No cross-hybridization occurred between the gene(s) encoding acetylcholinesterase in P. equorum and ace-1 from the free-living nematode Caenorhabditis elegans. The expression of a single cholinesterase form in P. equorum, unusual in free-living nematodes, could be due to parasitic life adaptation with resulting reduction of locomotor activity.
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PMID:Expression of a single dimeric membrane-bound acetylcholinesterase in Parascaris equorum. 948 77

Wild-type (wt) butyrylcholinesterase (BuChE) and the E197D and D70G mutants were inhibited by diisopropylfluorophosphate (DFP) or soman under standard conditions of pH, temperature and pressure. The effect of hydrostatic and osmotic pressures on the aging process of DFP-phosphorylated enzymes (diisopropylphosphoryl-BuChE (DIP-BuChE)) was investigated. Hydrostatic pressure strongly increased the rate of aging of wt enzyme. The activation volumes (deltaV*) for the dealkylation reaction was -150 ml/mol for DIP-wtBuChE. On the other hand, pressure had little effect on the aging of the DIP-E197D mutant and no effect on the DIP-D70G mutant, indicating that the transition state of the aging reaction (dealkylation of an isoproxy chain) was associated with an extended conformation/hydration change in wtBuChE but not in mutants. The rate of aging decreased with osmotic pressure, supporting the idea that water is important for stabilizing the transition state. Molecular dynamics simulations were performed on the wtDIP adduct to relate the kinetic data to hydration changes in the enzyme active site gorge. The pH dependence of the melting temperature (Tm) of native and soman-wtBuChE, as determined by differential scanning calorimetry (DSC), indicated that the stabilization energy of aged BuChE is mainly due to the salt bridge between protonated H438 and PO-, with pK(H438) = 8.3. Electrophoresis under high pressure up to 2.5 kbar showed that aged wtBuChE did not undergo pressure-induced molten globule transition unlike the native enzyme. This transition was not seen for the mutant enzymes, indicating that mutants are resistant to the penetration of water into their structure. Our results support the conclusion that D70 and E197 are major residues for the water/H-bond network dynamics in the active site gorge of BuChE, both residues acting like valves. In mutant enzymes, mutated residues function like check valves: forced penetration of water in the gorge is difficult, release of water is facilitated.
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PMID:Structural and hydration changes in the active site gorge of phosporhylated butyrylcholinesterase accompanying the aging process. 1042 35

The nontarget effects of temephos (as Abate 4E, 44.6% active ingredient) on fiddler crabs were examined on the salt marsh at Bombay Hook National Wildlife Refuge, near Dover, DE. Six 170 x 170-m plots were established; 3 were sprayed on 4 occasions at a rate of 1.5 fl oz/acre (0.054 kg active ingredient/ha) and 3 were controls. On each plot, marsh fiddler crab (Uca pugnax) populations were monitored by repeatedly counting the number of burrow holes in 2 counting areas marked out along tidal guts. One half of each counting area was covered with bird netting to evaluate sublethal toxic effects, which, if present, could result in increased susceptibility to bird predation. A statistically significant linear association was established between the number of holes and the number of crabs. No significant differences were found in the numbers of holes (or crabs) in the sprayed vs. control plots and in the covered vs. uncovered sections. However, survival of juvenile crabs in in situ bioassays was significantly reduced (16% lower) by the spraying. Median acetylcholinesterase activity in claw muscle of red-jointed fiddler crabs (Uca minax) collected 2 days after an operational spray with Abate 4E was significantly reduced (28% lower) compared to unsprayed crabs. In view of the toxicity to juvenile crabs and the cholinesterase inhibition, we recommend continued monitoring and research for nontarget impacts of Abate 4E on fiddler crabs to establish whether the reported level of cholinesterase inhibition results in acute or chronic toxicity.
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PMID:Effects of temephos (Abate 4E) on fiddler crabs (Uca pugnax and Uca minax) on a Delaware salt marsh. 1048 Jan 23

Wild-type human butyrylcholinesterase (BuChE) and Glu-197-->Asp and Asp-70-->Gly mutants (E197D and D70G respectively) were inhibited by di-isopropyl phosphorofluoridate under standard conditions of pH, temperature and pressure. The effect of hydrostatic and osmotic pressures on the aging process (dealkylation of an isopropyl chain) of phosphorylated enzymes [di-isopropylated (DIP)-BuChE] was investigated. Hydrostatic pressure markedly increased the rate of aging of wild-type enzyme. The average activation volume (DeltaV( not equal)) for the dealkylation reaction was -170 ml/mol for DIP wild-type BuChE. On the other hand, hydrostatic pressure had little effect on the aging of the DIP mutants (DeltaV( not equal)=-2.6 ml/mol for E197D and -2 ml/mol for D70G), suggesting that the transition state of the aging process was associated with an extended hydration and conformational change in wild-type BuChE, but not in the mutants. The rate of aging of wild-type and mutant enzymes decreased with osmotic pressure, allowing very large positive osmotic activation volumes (DeltaV not equal osm) to be estimated, thus probing the participation of water in the aging process. Molecular dynamics simulations performed on the active-site gorge of the wild-type DIP adduct showed that the isopropyl chain involved in aging was highly solvated, supporting the idea that water is important for stabilizing the transition state of the dealkylation reaction. Wild-type BuChE was inhibited by soman (pinacolyl methylphosphonofluoridate). Electrophoresis performed under high pressure [up to 2.5 kbar (1 bar=10(5) Pa)] showed that the soman-aged enzyme did not pass through a pressure-induced, molten-globule transition, unlike the native wild-type enzyme. Likewise, this transition was not seen for the native E197D and D70G mutants, indicating that these mutants are resistant to the penetration of water into their structure. The stability energetics of native and soman-aged wild-type BuChE were determined by differential scanning calorimetry. The pH-dependence of the midpoint transition temperature of endotherms indicated that the high difference in stabilization energy between aged and native BuChE (DeltaDeltaG=23.7 kJ/mol at pH 8.0) is mainly due to the salt bridge between protonated His-438 and PO(-), with pK(His-438)=8.3. A molecular dynamics simulation on the MIP adduct showed that there is no water molecule around the ion pair. The 'hydrostatic versus osmotic pressure' approach probed the importance of water in aging, and also revealed that Asp-70 and Glu-197 are the major residues controlling both the dynamics and the structural organization of the water/hydrogen-bond network in the active-site gorge of BuChE. In wild-type BuChE both residues function like valves, whereas in the mutant enzymes the water network is slack, and residues Gly-70 and Asp-197 function like check valves, i.e. forced penetration of water into the gorge is not easily achieved, thereby facilitating the release of water.
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PMID:Hydration change during the aging of phosphorylated human butyrylcholinesterase: importance of residues aspartate-70 and glutamate-197 in the water network as probed by hydrostatic and osmotic pressures. 1051 Mar 1

The prerequisite for the use of biomarkers of exposure as indicators of health risk is that the relationship between the biomarker and the health effects and the representation in time of the biomarker level are known. Some exposure biomarkers may be applied for the quantitative assessment of the amount of exposure. In this task, the half-time of the parameter measured is crucial, since it determines what length of time of exposure the result reflects. For reliable assessment of the exposure the species (e.g. metal, oxide or salt) has to be known. For some chemicals the estimation of exposure from biomonitoring is based on several studies with uniform results and is quite reliable, while for others the uncertainty is wide. Exposure biomarkers have been successfully used in the identification of exposed individuals and follow-up of exposure. For example, macromolecule adducts and mutagenicity in urine have been successfully applied to the identification of workers exposed to carcinogens and as indicators of changes of exposure. Biomarkers of renal effects of cadmium, lead effects on haemoglobin synthesis and organophosphate effects on cholinesterase activities have been well validated and are widely used in routine monitoring activities. However, effect markers for lead and cadmium offer little advantage over the analysis of the chemical itself and where accurate metal analysis is readily available, they have a limited use today. For the analysis of chromosomal aberrations, limited data are available suggesting that elevated frequencies may indicate a carcinogenic risk. In several instances, genotoxic effect monitoring has been used to identify groups of people exposed to hazardous chemicals and in the follow-up of improvements in industrial hygiene.
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PMID:Exposure and effect monitoring: a critical appraisal of their practical application. 1051 Dec 55

Different kinds of organophosphorous compounds (OP) are used as pesticides in Turkish agriculture. Suicidal, accidental, or occupational exposure may occur in developing countries. OP inhibit acetylcholinesterase (AChE) activities; on the other hand, serum paraoxonase (PON1) hydrolyzes the toxic metabolites of a variety of OP. In recent years, some studies have shown that PON1 activity is an important marker in individuals who are exposed to OP. Both serum cholinesterase and PON1 activities were measured spectrophotometrically from 18 male agricultural workers who were chronically exposed to azinphos methyl, chlorpyriphos, or malathion and other pesticides during cereal spraying, transportation, and storage. The individuals were classified according to PON1 phenotypes using the antimode 60% stimulation method to determine the dividing point between non-salt-stimulated, A type (homozygotes for the low-activity allele), and salt-stimulated AB (heterozygotes) and B types (homozygotes for the high-activity allele). A positive correlation was found between AChE activities and percent of PON1 stimulation. The individuals with phenotype A had the lowest enzyme activities. This study suggests that individuals with phenotype A might be more sensitive to OP-induced toxicity.
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PMID:Paraoxonase and acetylcholinesterase activities in humans exposed to organophosphorous compounds. 1063 39

A simple and rapid bioautographic enzyme assay on TLC plates has been developed for the screening of acetylcholinesterase and butyrylcholinesterase inhibition by plant extracts. Enzyme activity was detected by the conversion of naphthyl acetate into naphthol and the formation of the corresponding purple-coloured diazonium dye with Fast Blue B salt. Inhibitors of cholinesterases produced white spots on the dye-coloured background of the TLC plates. The alkaloids galanthamine and physostigmine, which are known inhibitors of acetylcholinesterase, were used to determine the sensitivity of the assay. Various plant extracts were tested using the bioassay.
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PMID:A rapid TLC bioautographic method for the detection of acetylcholinesterase and butyrylcholinesterase inhibitors in plants. 1189 7

The accepted mechanism of toxicity of many organophosphorous and carbamate insecticides is inhibition of acetylcholinesterase activity. In mammals, part of the toxicity assessment usually includes monitoring blood and/or brain acetylcholinesterase inhibition. Other tissues, however, contain cholinesterase activity (i.e. acetyl- and butyryl-cholinesterase), and the inhibition of that activity may be informative for a full appraisal of the toxicity profile. The present group of studies first optimized the variables for extraction and solubilization of cholinesterase activity from various rat tissues and then refined an existing automated method, in order to differentially assess acetyl and butyrylcholinesterase activity in those tissues. All these studies were conducted using tissues from untreated, Long-Evans, adult rats. The first studies determined the effect of Triton X-100 or salt (NaCl) on the extraction and solubilization of cholinesterase activity from retina, brain, striated muscle, diaphragm, and heart: phosphate buffer plus detergent (1% Triton X-100) yielded the highest activity for most tissues. For striated muscle, however, slightly more activity was extracted if the phosphate buffer contained both 1% Triton X-100 and 0.5 M NaCl. It was also noted that the degree of homogenization of some tissues (e.g. striated muscle) must be increased for maximal solubilization of all cholinesterase activity. Subsequent studies developed a method for assessing the level of acetylcholinesterase, butyrylcholinesterase and total cholinesterase activity in these tissues using an automated analyzer. In conclusion, automated assay of acetylcholinesterase activity in cholinergically innervated tissues in the rat (other than brain) is achievable and relatively convenient.
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PMID:Automated measurement of acetylcholinesterase activity in rat peripheral tissues. 1262 16

Human serum paraoxonase (PON1) and perhaps other mammalian paraoxonases catalyzes the hydrolysis of certain organophosphorus (OP) insecticides and nerve gases and so may alter significantly an individual's susceptibility to the toxicity of these chemicals. Serum PON1 exhibits a substrate dependent polymorphism and this polymorphism shows great interethnic variability. This study focused on the investigation of PON1, arylesterase and cholinesterase activities in 28 acute OP insecticide poisoning cases. Insecticide analysis were performed by GC-NPD and activities of enzymes were measured by using spectrophotometer. The activity levels for salt stimulated PON1, basal PON1 and arylesterase were found as 78.83 (35.39-186.13), 39.97 (2.49-80.43) micromol/min/l and 126.26 (36.34-288.24) mmol/min/l respectively. On the other hand the activity levels for butyrylcholinesterase (BTC) and acetylcholinesterase (AchE) were found as 797.23 (106.3-3823)U/l and 4.65 (0.21-30.29)U/ml. There was a correlation between percent stimulation of PON1 and BTC activities (r=0.446, P<0.05), but this correlation was lower than in cases who exposed to OP insecticides chronically. As a conclusion, in chronic and acute OP exposure, both PON1 level and phenotype must be taken into consideration.
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PMID:Human serum paraoxonase (PON1) activity in acute organophosphorous insecticide poisoning. 1274 1

A major result of incoherent elastic neutron-scattering experiments on protein powders is the strong dependence of the intramolecular dynamics on the sample environment. We performed a series of incoherent elastic neutron-scattering experiments on lyophilized human butyrylcholinesterase (HuBChE) powders under different conditions (solvent composition and hydration degree) in the temperature range from 20 to 285 K to elucidate the effect of the environment on the enzyme atomic mean-square displacements. Comparing D(2)O- with H(2)O-hydrated samples, we were able to investigate protein as well as hydration water molecular dynamics. HuBChE lyophilized from three distinct buffers showed completely different atomic mean-square displacements at temperatures above approximately 200 K: a salt-free sample and a sample containing Tris-HCl showed identical small-amplitude motions. A third sample, containing sodium phosphate, displayed highly reduced mean-square displacements at ambient temperature with respect to the other two samples. Below 200 K, all samples displayed similar mean-square displacements. We draw the conclusion that the reduction of intramolecular protein mean-square displacements on an Angstrom-nanosecond scale by the solvent depends not only on the presence of salt ions but also on their type.
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PMID:The influence of solvent composition on global dynamics of human butyrylcholinesterase powders: a neutron-scattering study. 1511 28


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