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At least 19 recordsLinked to original sources
PubMed1998

cDNA cloning, in vitro expression, and biochemical characterization of cholinesterase 1 and cholinesterase 2 from amphioxus--comparison with cholinesterase 1 and cholinesterase 2 produced in vivo.

We have isolated cDNAs coding for the complete amino acid sequences of cholinesterase 1 (ChE1) and cholinesterase 2 (ChE2) from amphioxus. Both ChE transcripts have the characteristics of H-type catalytic subunits, which are inserted in the membrane via an ethanolamine-glycan-phosphatidylinositol anchor. The members of the catalytic triad of ChEs, the three pairs of cysteine residues involved in intrachain disulfide bonding, a cysteine near the carboxy terminal of both sequences, which could mediate interchain disulfide bonding, and 11 of the 14 aromatic amino acids that line the catalytic gorge of AChE are conserved. A remarkable difference between the two enzymes is in the region of the acyl-binding pocket, which plays an important role in determining substrate specificity in cholinesterases. ChE2 contains a sequence that resembles the acyl pocket of invertebrate ChE, while the acyl-binding site of ChE1 is novel. There are also differences between the two enzymes in the peripheral anionic site, which mediates inhibition by certain ligands. In vitro expression in COS-7 cells demonstrates that ChE2 hydrolyzes acetylthiocholine almost exclusively, while ChE1 hydrolyzes both acetylthiocholine and butyrylthiocholine. Both enzymes are inhibited comparably by BW284c51, but ChE1 is considerably more resistant to inhibition by propidium, ethopropazine, and eserine than is ChE2. Velocity sedimentation indicates that ChE1 and ChE2 are present as amphiphilic and nonamphiphilic G2 forms in vivo and in vitro. Another molecular form, which sediments at 17 S, is also present in vivo. Nondenaturing gel electrophoresis in conjunction with digestion by phosphatidylinositol-specific phospholipase C demonstrates that the vast majority of ChE1 and ChE2 is present as ethanolamine-glycan-phosphatidylinositol-anchored G2 forms in vivo. ChE1 also possesses an ethanolamine-glycan-phosphatidylinositol-anchor in vitro; however, ChE2 produced in vitro could not be detected on nondenaturing gels.

Acetylthiocholine↗
PubMed1997

Red cell acetyl cholinesterase and plasma cholinesterase activity and genetic variants of plasma cholinesterase in northwest Indian adults.

The plasma cholinesterase (PChE) and red cell acetyl cholinesterase (AChE) activities are indicators of exposure to organophosphates. We studied their distribution in unexposed Northwest Indian adults by measuring them in 120 men and 111 women by Ellman's and Kalow's method, respectively. We also determined genetic variability of plasma cholinesterase in 193 subjects (male = 111, female = 82). The mean +/- (SD) AChE levels in population, men and women, were 34.97 +/- 13.66, 35.05 +/- 12.42, 34.88 +/- 14.89 nmol/mg Hb/min, whereas PChE was 0.448 +/- 0.173, 0.435 +/- 0.163, 0.462 +/- 0.183 ku/l, respectively. When compared for sex, no significant difference could be found for red cell AChE and PChE activity. However, on 2-way analysis of variance (ANOVA) adjusted for age classification, the levels of both AChE and PChE were significantly higher in groups above the age of 30 years as compared to below 30 years (t = 3.08, p < 0.01, t = 2.82, p < 0.05), respectively. Seven genetic variants of PChE could be detected in males, whereas in females 6 genetic variants were found.

Acetylcholinesterase↗
PubMed1982

Inhibitory effect of acephate (N-acetyl O, S-dimethyl thiophosphoramide) on serum cholinesterase--effect of acephate on cholinesterase.

The Lineweaver-Burk plot of the activity of human serum cholinesterase against the concentration of butyrylthiocholineiodide was shown by two intersecting lines. The Hill plot of cholinesterase activity was linear over the entire range of the substrate concentration. The n value, an interaction coefficient, was less than 1.0 (about 0.8). These results suggest that cholinesterase has multiple substrate binding sites. Acephate, one of the organophosphorous insecticides, inhibited the activity of cholinesterase. Acephate at concentration under 1.25 mM (about 230 ppm in serum) did not inhibit the activity of cholinesterase. The minimum concentration of acephate inhibition of cholinesterase activity was at 2.5 mM. An equilibrium constant(K) can be used as an indicator of inhibitory effect on cholinesterase. The serum cholinesterase activity of workers who were exposed to acephate is not affected when the concentration of acephate in serum is less than 200 ppm. This result suggests that the activity of serum cholinesterase is not an accurate indicator of the exposure of the low toxic insecticides, e.g. acephate. The inhibitory effect of acephate on cholinesterase decreased after the incubation with S-9 mixture. This result suggests that a part of acephate is metabolized to inactive substances in the liver.

Cholinesterase Inhibitors↗
PubMedDate not supplied

Comparison of red cell cholinesterase and plasma cholinesterase activities in early detection of organo-phosphorus toxicity in exposed industrial workers in Port Harcourt, Nigeria.

BACKGROUND: The Niger Delta region of Nigeria has a high concentration of companies using organo-phosphorus compounds with workers who have been exposed to these compounds for varying lengths of time resulting in toxic manifestations in some of the workers. Studies have revealed that plasma cholinesterase and red cell cholinesterase levels are reduced following organo-phosphorus toxicity. This study looks at cholinesterase levels in plasma and red cell in the occupationally exposed groups and control with a view to determining which will be more useful in the early detection of organo-phosphorus toxicity. METHOD: Fourty seven subjects with early symptoms of organo-phosphorus toxicity who have worked for more than 4 years with organo-phosphorus compounds were selected from five companies localized around the same area in Port Harcourt. Fifty subjects who do not work directly with organo-phosporus compounds from the same companies as the 47 workers above but not working directly in the organo-phosphorus units were also studied while 50 persons working in the civil service were recruited as controls. The kinetic colorimetric method was used for measuring plasma and red cell cholinesterase activity Result: The results showed significant reduction in the mean plasma cholinesterase activity in the chronically exposed subjects (4614. +/- 532) who showed symptoms of toxicity when compared with that of the control group (8095 +/- 575). There was no statistical difference in the mean red cell cholinesterase activity of the chronically exposed group (7998. +/- 948) when compared with that of the control (8115. +/- 712) P > 0.05 CONCLUSION: The effect of organo-phosphorus poisoning occurs early and is more marked in plasma cholinesterase than in the red cell cholinesterase. Plasma cholinesterase is thus more useful in early detection of organo-phosphorus toxicity than red cell cholinesterase.

Adult↗
PubMed1994

Interlaboratory cholinesterase determinations and the effect on the results of statistical evaluation of cholinesterase inhibition.

Cholinesterase activity is often a key parameter in the regulatory assessment of cholinesterase-inhibiting agents such as organophosphorous and carbamate pesticides. Thus, the nature and characteristics of the methodology involved in the measurement of plasma (PChe), erythrocyte (R Che), and brain (BChe) cholinesterase activity takes on a heightened degree of importance. In this study an interlaboratory comparison of cholinesterase activity as determined by various laboratories was conducted in order to assess the influence that different methodologies may have on the results of statistical evaluation of cholinesterase inhibition. RChe, PChe, and BChe from animals exposed to fenthion, a known cholinesterase inhibitor, were determined at 8 different laboratories with experience in cholinesterase determination. Seven different instruments and 5 different assay procedures were employed. Marked differences in both the magnitude of inhibition measured and its designation as a statistically significant difference often occurred between laboratories using both the same as well as different methods of cholinesterase analysis. These findings illustrate the importance of considering not only the sensitivity of a given method of analysis, but also the influence of inter- and intra-laboratory variation on statistically responsive aspects of the data profile itself (i.e., precision, sample size, etc.) when establishing regulatory levels (i.e., Reference Doses (RfDs), Health Advisory Levels (HALs), etc.) on the basis of a cholinesterase no-observed- or lowest-observed-effect level (NOEL, LOEL).

Analysis of Variance↗
PubMed2005

Pharmacokinetics and pharmacodynamics of mivacurium in patients phenotypically homozygous for the atypical plasma cholinesterase variant: effect of injection of human cholinesterase.

BACKGROUND: In patients homozygous for atypical plasma cholinesterase, mivacurium causes a long-lasting neuromuscular block, but injection of human cholinesterase has been proven effective in antagonizing the block. The purpose of this study was to evaluate the pharmacodynamics and pharmacokinetics of mivacurium in such patients, as well as the effect of cholinesterase injected early or late after mivacurium. METHODS: Eleven patients phenotypically homozygous for the atypical variant received 0.075 mg/kg (1 patient) or 0.15 mg/kg (10 patients) mivacurium. The neuromuscular block was monitored using train-of-four nerve stimulation and mechanomyography. Cholinesterase, 2.8-10.0 mg/kg, was administered approximately 30 or 120 min after mivacurium. The times to different levels of neuromuscular recovery and the venous concentrations of the isomers of mivacurium were measured. RESULTS: Injection of cholinesterase increased plasma cholinesterase activity to normal and the clearances of the active isomers and the elimination rate constants by a factor of 10-15. The first response was seen in 13.5 min (3.7-44.2 min). Time to a train-of-four ratio of 0.8 ranged from 30 to 60 min (n = 6). Neostigmine injected after cholinesterase shortened recovery further, and a train-of-four ratio of 0.8 was reached in 10-30 min. CONCLUSION: As expected, the duration of action of mivacurium is markedly prolonged in homozygous atypical patients. Injection of cholinesterase significantly increases the metabolism of mivacurium, leading to a shorter duration of action. Injection of neostigmine after the administration of cholinesterase speeds up recovery.

Adolescent↗
PubMed1990

Immunoreactive plasma cholinesterase (EC 3.1.1.8) substance concentration, compared with cholinesterase activity concentration and albumin: inter- and intra-individual variations in a healthy population group.

Substance concentrations of plasma cholinesterase (EC 3.1.1.8) were measured in 94 healthy individuals without occupational exposure to known inhibitors (six samples from each individual). Immunoreactive cholinesterase substance concentrations showed an inter-individual variation corresponding to CVtotal = 22% (mean: 5.01 mg/l, SD: 1.11 mg/l). Intra-individual variations of immunoreactive cholinesterase substance concentration were correlated (r = 0.36) to intra-individual variation of albumin. Estimated by a repeated-measures analysis of variance, the observed intra-individual variation of cholinesterase substance concentration corresponded to CV = 8.8% (SD: 0.44 mg/l), which together with a CVerror = 6% (within and between runs), implies a biological intra-individual variation of cholinesterase substance concentration corresponding to CVintra = 6.4%. Specific catalytic activity (kU/mg immunoreactive cholinesterase) was influenced by the ChE-1 phenotype (phenotype U: 1.58 kU/mg, phenotype UA: 1.22 kU/mg), but not by body weight, height, age, and sex. Observed intra-individual variation of specific catalytic activity corresponded to 6.4% (SD: 0.10 kU/mg), which together with an estimated CVerror = 6.2% implies the biological intra-individual variations of specific catalytic cholinesterase activity to be insignificant. The insignificant CVintra makes specific catalytic cholinesterase activity a rational quantity for evaluation of unexpected fluctuations of cholinesterase activity concentrations.

Adult↗
PubMed1973

Cholinesterases from plant tissues: I. Purification and characterization of a cholinesterase from mung bean roots.

A cholinesterase was purified 36-fold from mung bean (Phaseolus aureus) roots by a combination of differential extraction media and gel filtration. The enzyme could be effectively extracted only by high salt concentration, indicating that it is probably membrane-bound. Methods used for assaying animal cholinesterases were tested, two of which were adapted for use with the bean cholinesterase. The bean enzyme hydrolyzed choline and noncholine esters but showed its highest affinity for acetylcholine and acetylthiocholine. The pH optimum was 8.5 for acetylthiocholine and 8.7 for acetylcholine. The Michaelis constants were 72 and 84 mum for acetylcholine and acetylthiocholine, respectively. The cholinesterase was relatively insensitive to eserine (half-maximum inhibition at 0.42 mm) but showed high sensitivity to neostigmine (half-maximum inhibition at 0.6 mum). Other animal cholinesterase inhibitors were also found to inhibit the bean enzyme but most of them at higher concentrations than are generally encountered. Choline stimulated enzymatic activity. The molecular weight of the cholinesterase was estimated to be greater than 200,000, but at least one smaller form was observed. It is suggested that the large form of cholinesterase is converted to the smaller form by proteolysis.

Journal Article↗
PubMed1980

A reliable way of estimating cholinesterases from whole blood in the presence of anti-cholinesterases.

A method for the determination of cholinesterases [1] has been adapted to monitor these enzymes in the presence of anti-cholinesterase insecticides. The cholinesterases in blood samples, which were dried on filter papers, could be eluted with water (plasma cholinesterase) and with 1% Triton X-100 (erythrocyte acetylcholinesterase) with complete recovery of the enzyme activity. The samples could be stored at room temperature for at least two weeks and in a refrigerator more than six weeks without a decreased efficiency of elution from the filter paper. It was found that if blood samples to which the two insecticides, used to test the validity of the method, had been added, were stored on filter paper at room temperature or deep frozen for at least one week, there was the same inhibition of the cholinesterases as at the start of the experiment. The samples stored at room temperature in tubes, recovered maximally within a day. This modified method of cholinesterase determination will be especially suitable when samples have to be mailed to laboratories making the analysis.

Cholinesterase Inhibitors↗
PubMed1999

Inhibition of neurite outgrowth from chick sympathetic neurons by cholinesterase inhibitors is not mediated by binding to cholinesterases.

Several studies have suggested a role for cholinesterases in regulating neurite outgrowth. Some acetylcholinesterase (AChE) inhibitors can inhibit neurite outgrowth, but it is unclear if this is due to inhibition of AChE. In this study, the effect of cholinesterase inhibitors on neurite outgrowth from chick sympathetic neurons was examined. Very high (micromolar) concentrations of tacrine and BW284c51 were needed to inhibit neurite outgrowth. In contrast, nanomolar concentrations were required to block cholinesterase activity. No correlation was found between the type of inhibitor or potency of cholinesterase inhibition and inhibition of neurite outgrowth. Both tacrine and BW284c51 were neurotoxic at concentrations that inhibited outgrowth. Therefore, the action of cholinesterase inhibitors on neurite outgrowth may be due to non-specific toxicity rather than to cholinesterase binding.

Animals↗
PubMed1983

Plasma cholinesterase and trophoblastic disease. Gestational trophoblastic disease and reduced activity of plasma cholinesterase.

A case of prolonged action of suxamethonium in a patient with gestational trophoblastic disease is reported. Postoperatively the patient was found to have markedly reduced plasma cholinesterase activity (363 IU/litre) with a normal cholinesterase phenotype. Consequently plasma cholinesterase activity and phenotype were measured in six other patients with the condition and these results compared with those of 22 patients with normal first trimester pregnancies undergoing therapeutic abortion. Plasma cholinesterase phenotype was normal in all patients studied. The activity was significantly decreased (p less than 0.05) from the normal range (620-1370 IU/litre) in all patients with trophoblastic disease. In the 22 patients with normal pregnancies, 14 had activity values in the abnormal range (less than 620 IU/litre) while the mean cholinesterase activity of the group as a whole was significantly decreased (561.8 IU/litre, p less than 0.05) below the normal range. These results confirm the presence of a decrease in plasma cholinesterase activity in early pregnancy and provide new evidence for a decrease in activity in a pseudopregnancy state.

Adult↗
PubMed1990

The effect of bambuterol on plasma cholinesterase activity and suxamethonium-induced neuromuscular blockade in subjects heterozygous for abnormal plasma cholinesterase.

Bambuterol is a new bronchodilator which is also a reversible inhibitor of plasma cholinesterase. In patients with normal plasma cholinesterase genotype, bambuterol prolongs suxamethonium-induced neuromuscular blockade. In the present study, we investigated the interaction of bambuterol and suxamethonium in nine patients heterozygous for abnormal plasma cholinesterase during anaesthesia with fentanyl, thiopentone, halothane and nitrous oxide in oxygen. The patients (seven E1uE1a and two E1uE1s) were given 20 mg of bambuterol orally 2 h before anaesthesia. Suxamethonium 1 mg.kg-1 was given for tracheal intubation. The neuromuscular function was monitored using train-of-four (TOF) stimulation of the ulnar nerve and a force displacement transducer. Plasma cholinesterase activity decreased in all patients following bambuterol (P less than 0.001). In patients with genotype E1uE1a, median time to 90% recovery of twitch height and TOF ratio greater than or equal to 0.7 (37.5 min) was prolonged compared to 28 E1uE1a patients not treated with bambuterol (14.0 min) (P less than 0.001). Four of these patients developed a phase II block apparently not correlated to plasma cholinesterase activity. In the E1uE1s; patients, full recovery was seen after 22.0 and 31.4 min, respectively. It is concluded that in patients heterozygous for abnormal plasma cholinesterase, bambuterol 20 mg taken 2 h before anaesthesia causes a 2-3 times prolongation of the neuromuscular blockade following suxamethonium 1 mg.kg-1 and in some patients a phase II block.

Adult↗
PubMed1980

Hen's egg yolk cholinesterase. Purification, characterization and comparison with hen's liver and blood plasma cholinesterase.

The cholinesterase (acylcholine acylkhydrolase, EC 3.1.1.8) of chicken egg yolk was partly purified and characterized. It was compared to homologous enzymes of liver and blood plasma of laying hens. During gel filtration, yolk and liver cholinesterase were resolved into two fractions. Blood plasma cholinesterase showed one form only, identical with yolk and liver cholinesterase 1 *** (EC 3.1.1.8). This form has an Mr of 440 000 and may be a tetramer of a cholinesterase form present in yolk and liver (Mr 104 000). Substrate specificity, pH optima, Km values, the influence of effectors (ammonium derivatives, choline, eserine, fluoride), gel filtration, gel electrophoresis, isoelectric focusing and affinity chromatography, all point to a very close similarity, if not identity, of the corresponding forms.

Animals↗
PubMed1990

Plasma cholinesterase activity in a healthy population group with no occupational exposure to known cholinesterase inhibitors: relative influence of some factors related to normal inter- and intra-individual variations.

Inter-individual variations of plasma cholinesterase were analysed in 193 apparently healthy volunteers (122 males, 71 females) with no known occupational exposure to cholinesterase inhibitors. Multiple regression analysis and analysis of variance showed statistically significant effects on the individual plasma cholinesterase activity by body weight, height, sex, and ChE-1 phenotype (but not by age or electrophoretic phenotype). Varying body weight explained one-fourth of the observed biological variance (s2total). The intra-individual variations during an 8-month period varied substantially from one individual to another (3% to 41% of the subject's mean activity); a repeated-measures analysis of variance showed a within-person variance (s2intra) = 5% of s2total. Intra-individual variation was uninfluenced by the variables that influence the inter-individual variance. A model for a 'standardized' plasma cholinesterase in which the combined effects of the four significant variables, ChE-1 phenotype, sex, body weight, and height are eliminated, is proposed for comparisons of plasma cholinesterase activities in unmatched population groups, e.g. within environmental or occupational medicine.

Adult↗