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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)

The activity of locust ganglia cholinesterase is found to depend on concentrations of acetylthiocholine (ATC), propionylthiocholine (PTC) and butyrylthiocholine (BTC); that of carboxylesterase--on concentration of p-nitrophenylacetate (25 degrees, pH 7,5). The activity of cholinesterase is inhibited by an excess of ATC and BTC, but is unaffected by an excess of PTC. At concentrations greater than 0.01 M PTC is hydrolyzed faster than ATC at optimal (1.10(-3) M) concentration. The cholinesterase hydrolysis of BTC proceeds slower than that of ATC and PTC. The bimolecular constants (kII) of the rate of cholinesterase and carboxylesterase interaction with structurally different organophosphorus inhibitors (OPI) were determined. It was found that methylsulfomethylates of O-alkyl-S (beta-ethylmercaptoethyl) methylthiophosphonates are stronger inhibitors of cholinesterase than carboxylesterase; on the contrast, their uncharged analogs are stronger inhibitors of carboxylesterase, since the substitution of the sulfide sulphur for the sulphonic one strongly decreases the anticholinesterase activity and slightly increases the anticarboxylesterase activity of these OPI. O-alkyl-S (carbomethoxymethylmercaptomethyl) methylthiophosphonates inhibit carboxylesterase stronger than cholinesterase. The inhibitory activity of diisopropylthiophosphates towards cholinesterase is much lower than that of the corresponding diethylthiophosphates, while the activity of the former towards carboxylesterase is approximately the same as the activity of diethylthiophosphates or more strongly pronounced. Diisopropylfluorophosphate is a potent inhibitor of carboxylesterase. The data obtained provide evidence for differences in the structure of the active sites of cholinesterase and carboxylesterase. The carboxylesterase has no anionic sites. Moreover, the active surface of this enzyme interacting with the leaving part of OPI possesses, a site which prevents the absorption of cationic OPI and favours the interaction with the OPI containing the carboxyether group. The esterastic site of carboxylesterase is larger than that of cholinesterase and can predominantly interact with OPI having a bulky phosphoryl part.
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PMID:[Properties of cholinesterase and carboxylesterase from locust ganglia]. 54 51

It was shown that locust cholinesterase splits various thiocholine esters with different rate. Hydrolysis of p-NPA is due to the effect of carboxylesterase. The latter differs from cholinesterase by a low sensitivity to eserine and cation-containing organophosphorus inhibitor methylsulfomethylate-O-ethyl-S-(beta-ethylmercaptoethyl) methylthiophosphonate, as well as by higher sensitivity to triorthocresylphosphate. The results obtained are discussed in relation to possible differences of the active surface of the enzymes studied.
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PMID:[Properties of the nervous tissue cholinesterase and carboxylesterase in the locust, Locusta migratoria]. 67 90

The ontogeny of esterase isozymes in Brachydanio rerio (zebra danio), Brachydanio albolineatus (pearl danio), and hybrids formed by their reciprocal crosses was investigated using polyacrylamide disc electrophoresis. Seven esterase isozymes were identified in each species from the unfertilized egg stage to nine days posthatch. Electrophoretic analysis of qualitative changes in enzyme pattern indicated that some esterases were present at all stages of development while other esterases abruptly appeared at a specific stage of morphological differentiation. The esterases of both species were classified on the basis differential substrate and inhibitor specificities. In developing hybrids formed by B. rerio eggs inseminated with B. albolineatus sperm, the maternal isozyme pattern persisted until Stage 17 (gastrulation). Embryonic extracts from Stage 17 onward showed a slow-moving, DFP-sensitive carboxylesterase of paternal origin. In developing hybrids formed by B. albolineatus eggs inseminated with B. rerio sperm, a paternal contribution to the esterase pattern was probably present by the end of gastrulation; esterase activity of distinctively paternal origin was present by Stage 22 (retinal pigmentation) The maternal contribution to the total esterase profile appeared to remain high through hatching. Additional evidence for gene activity at gastrulation was obtained in experiments utilizing actinomycin-D and cycloheximide. Results of exposing embryos of B. rerio to 15 mug/ml of actinomycin-D indicated that transcription of the template RNA coding for cholinesterase occurred during gastrulation or some 20-30 hours prior to the appearance of the isozyme at Stage 22. This template RNA was translated sometime during that 10-hour interval immediately preceding Stage 22.
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PMID:Esterase isozyme patterns in developing embryos of Brachydanio rerio (zebra danio), Brachydanio abolineatus (pearl danio), and their hybrids. 83 81

A maximum of 22 bands comprising four esterase subgroups--acetylesterase, carboxylesterase, cholinesterase, and acetylcholinesterase--were detected following electrophoresis of lesser snow goose sera on polyacrylamide gels. A minimum of seven structural genes was surmised to be involved in the biosynthesis of these enzymes following physiochemical characterizations. The genetic variability of these loci was calculated to be 1.25% average heterozygosity, while 14.3% of the loci were polymorphic. These estimates of genetic variability were substantially lower than those reported for other vertebrate species. The low degree of genetic variability found in snow goose serum esterases coupled with the extensive protein multiplicity observed may possibly reflect an adaptive strategy based on "biochemical plasticity" rather than genic heterozygosity for this species. The nature of evolutionary forces acting upon multiple enzyme systems such as esterases is discussed. The concept of "conditional neutrality" is introduced and defined within this context.
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PMID:Isoenzyme status and genetic variability of serum esterases in the lesser snow goose, Anser caerulescens caerulescens. 92 42

Eccrine sweat collected from the human skin surface contains at least five different esterases. One of them is a cholinesterase. A non-specific carboxylesterase with the electrophoretic mobility of an alpha-globulin appears to be a serum protein. Besides this, there are two isoenzymes of human origin migrating with the same electrophoretic mobility as gamma-globulins. These two isoenzymes are immunologically identical with a non-specific carboxylesterase occurring in numerous organs and body fluids. Lipase activity could not be demonstrated.
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PMID:Immunological demonstration of multiple esterases in human eccrine sweat. 95 42

A number of enzymes, presumably secreted by larvae of B. microplus under natural feeding conditions, have been investigated in the skin of previously unexposed calves 4 h after infestation at the attachment site. Carboxylic ester hydrolase activity was demonstrated in the dermis, immediately adjacent to the mouthparts, or in the attachment cone, depending on substrate and reaction pH. The carboxylic ester hydrolase acting on naphthol AS-D acetate (2-acetoxy-3-naphthoic-O-toluidide) at pH 7-1 was characteristically found in the dermis and not in the attachment cone. The use of specific inhibitors showed that this enzyme was primarily a B-esterase or carboxylesterase with possibly a small portion of C-esterase or acetylesterase. It is postulated that carboxylic ester hydrolase could contribute to the dilation observed in the subepidermal capillaries adjacent to the attachment sites of unexposed animals, through the formation of plasma kinins. Other enzymes demonstrated in the dermis, adjacent to the mouthparts, were triacylglycerol lipase, as an aggregated deposit, and small amounts of aminopeptidase (microsomal) and monophenol monooxygenase. Aminopeptidase (microsomal) was also demonstrated in the attachment cone or adjacent epidermis, according to the substrate used. No activity was found in the host tissue, in association with the attachment site, for either alkaline or acid phosphatase, acetylcholinesterase or cholinesterase, peroxidase or amine oxidase (flavin-containing), despite the intense histochemical reaction for the latter in the tissues of larvae.
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PMID:Boophilus microplus: characterization of enzymes introduced into the host. 102 62

By means of starch gel electrophoresis blood plasma esterases in sheep of different breeds were studied. It is shown that the esterase pattern is a poly-enzyme system consisting of at least three enzymes: arylesterase, carboxylesterase and choline esterase. Postnatal changes of esterase pattern in sheep blood plasma were also studied. Polymorphism on substrate specificities is described, which is expressed in the fact that different arylesterase variants have different affinity to alpha- and beta-isomers of carbone ethers of naphtol. The breeding test suggests that two allelic autosomal genes, reffered to as Es-1a and Es-1b, control the substrate specificity of arylesterase in sheep. The data are discussed in connection with Es-1a and Es-1b gene expression in heterozygous sheep, with the effect of (mosaic) dominance.
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PMID:[Genetic control of the substrate specificity of sheep plasma arylesterase]. 123 33

The bases of using blood enzyme activity measurements [e.g. AChE, non-specific cholinesterase (BChE), carboxylesterase] as markers of organophosphate ester (OP) exposure are inhibition of activity by the binding of OPs to serine active sites in the enzymes, and the accessibility of the enzymes in RBCs and serum. The methods used to determine esterases in the blood of humans, experimental animals, and wildlife are outlined with emphasis on the acetylcholinesterase (AChE) of the red blood cell. Adaptations of an acetylthiocholine ester assay of Ellman et al. (1961) are common, but other colorimetric procedures, radiometric assays, and pH methods are also in use. Optimized, standardized methods are needed to assess exposures and provide a solid basis for risk assessment analyses. Useful adjuncts to ChE measurements are oxime reactivation tests and assay of neuropathy target esterase, an enzyme associated with organophosphate-induced delayed neuropathy. Determination of urinary metabolites compliments, but does not substitute for, the information obtained from blood ChE studies. Future assays are likely to involve antibodies to OP-protein complexes. Improvements in techniques permit the detection of small decreases in ChE activities. Whether or not such small decreases in ChE activities can, by themselves, constitute an adverse effect for input into risk assessment analyses is a controversial matter.
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PMID:Blood esterase determinations as markers of exposure. 141 Jun 89

Activities of enzymes cholinesterase (ChE) and carboxylesterase (CaE) were assayed in serum, liver microsomes and three regions of brain, viz; cerebrum, cerebellum and brain stem (with mid brain) in male albino rats at 0.5 and 2 h periods after administration of 1/2 LD 50 dose of soman (0.22 mg/kg) intraperitoneally in olive oil as vehicle. At 0.5 h, in serum, ChE activity declined to 33% of its initial level whereas CaE activity was almost completely inhibited. However, in the liver microsomes at this period, ChE activity was greatly inhibited (18% of initial level) whereas CaE activity was nearly unaffected. At 2 h period, both the enzymes in the serum were almost completely inhibited. In the brain regions (excepting in cerebellum), both the enzymes were nearly similarly inhibited (by 55% to 65% of the initial level) at both the periods. The time related differential response of these two beta-esterases in acute soman intoxication probably occurred in the peripheral tissues like blood and liver but not in the CNS.
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PMID:Effect of soman administration on beta-esterases in blood, liver microsomes and brain regions of rats. 147 52

Carbaryl, a carbamate insecticide, exerts its toxic effect in animals by inhibiting the activity of neural acetylcholinesterase. Differences in sensitivity of this enzyme to inhibition were studied after intraperitoneal administration to chickens and rats. A dose of 900 mg/kg to chickens and 70 mg/kg to rats caused equivalent inhibition of brain cholinesterase activities (57% +/- 6 and 47% +/- 4, respectively) 60 min after administration, which was the time of maximal cholinergic signs. Signs of toxicity (salivation, respiratory distress, muscle tremors and weakness) were more pronounced in rats than in chickens when brain acetylcholinesterase was inhibited to the same extent in both species. Carboxylesterase activities in brain, liver, and plasma were also inhibited 60 min after administration of carbaryl to chickens and rats. Activities of enzymes associated with hepatic microsomes were unaffected. Specific activities of brain esterases, including acetylcholinesterase, carboxylesterase and neurotoxic esterase, were higher in untreated chickens than in untreated rats. Specific activities of liver esterases (carboxylesterase, A-esterase) were, however, 4- and 10-fold lower in untreated chickens than in untreated rats. Total clearance of carbaryl in the chicken, determined after intravenous administration of 5 mg/kg, was 0.26 +/- 0.02 l/kg/min. This value is 5.7 times higher than that reported for the rat, indicating that the relatively lower activities of esterases in the liver of chickens did not affect the clearance of this chemical in the avian species.
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PMID:Toxicity and toxicokinetics of carbaryl in chickens and rats: a comparative study. 150 71


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