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)

Cell-bound acetylcholinesterase (AChE) was found to be an early differentiation marker on embryonic chick skeletal myoblasts in mixed primary cell cultures. AChE biosynthesis was detected and characterized by (a) a sensitive microtiter assay, (b) use of selective inhibitors, and (c) with mono- and polyclonal antibodies. Both secreted and cell-bound AChE appeared on the first day in culture, at a time when no muscle cell fusion was observed. Characterization of this enzyme revealed that true AChE was bound and secreted by myoblasts. BW284c51, which permeates cell membranes poorly, inhibited all the cell-associated AChE activity on myoblasts, suggesting that the activity measured was on the outer cell surface. On the other hand, fibroblasts appeared to have no or very little bound enzyme and the low level of secreted enzyme activity had the characteristics of pseudo-, or butyrylcholinesterase. Polyclonal anti-Torpedo californica electroplax AChE antibody and several monoclonal antibodies were found to bind specifically to chick myoblasts. Since the cells had not been made permeable before antibody binding, a membrane-bound form of the enzyme was most likely being detected. The cell-bound true AChE was present in identifiable quantities from the first day of culture. Membrane-bound AChE can thus serve as an early differentiation marker for embryonic chick myoblasts in mixed primary cultures.
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PMID:Membrane-bound acetylcholinesterase: an early differentiation marker for skeletal myoblasts. 147 43

The three-dimensional structure of human serum butyrylcholinesterase (BuChE) was modeled using a computer-based amino acid replacement strategy and the known coordinates of crystallized acetylcholinesterase (AChE) from Torpedo californica. The BuChE model was then energetically minimized with dynamic iterations of an adopted basis Newton-Raphson algorithm and the program CHARMM. Hypothetical glycosylation of this structure based upon the known carbohydrate composition of the enzyme was also performed. The glycosylated, minimized model predicts that the tertiary structure of BuChE could be very similar to AChE but that the entrance of the narrow channel leading toward its active site triad probably differs. All nine of the known N-linked oligosaccharides of BuChE are predicted to occur away from the putative active site channel and most are located on one face of the monomer.
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PMID:A computer model of glycosylated human butyrylcholinesterase. 148 44

A series of N-aryl-2-[[[5-[(dimethylamino)methyl]-2- furanyl]methyl]thio]ethylamino analogs of the H2-antagonist, ranitidine, was synthesized and the abilities of the compounds to alleviate the cholinergic deficit characteristic of Alzheimer's disease evaluated. The compounds were initially tested for their ability to inhibit human erythrocyte acetylcholinesterase activity in vitro. Selected compounds were further evaluated for butyrylcholinesterase inhibition, M1 and M2 cholinergic receptor binding, potentiation of ileal contractions, and the ability to elevate brain acetylcholine levels in mice. The analogs were compared to tetrahydroaminoacridine and to a recently reported series of bis-[[(dimethylamino)methyl]furans]. The N-aryl-2-[[[5-[(dimethylamino)methyl]-2- furanyl]methyl]thio]ethylamine derivatives were generally comparable to tetrahydroaminoacridine and the bis[[(dimethylamino)methyl]furans] in acetylcholinesterase inhibition, M1/M2 receptor binding, and the potentiation of ileal contractions, while being more potent inhibitors of acetylcholinesterase than butyrylcholinesterase. The 4-nitro-3-pyridazinyl analog, 26, was notable in demonstrating a potent and selective binding to the M2 receptor, with an M2 IC50/M1 IC50 of 0.060. Compounds in which the substituents on the dinitro-N-aryl moiety were relatively small were the best at inhibiting acetylcholinesterase in vitro. The N-aryl-2-[[[5-[(dimethylamino)methyl]-2- furanyl]methyl]thio]ethylamines in general, and those with small N-aryl substituents in particular, were superior to the bis[[(dimethylamino)methyl]furans] in elevating brain ACh levels in mice, probably due to enhanced distribution into the CNS. The 1,5-difluoro-2,4-dinitrophenyl analog, 8, resulted in the largest elevation in brain acetylcholine levels, affording a 53% increase at 88 mg/kg.
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PMID:Synthesis and cholinergic properties of N-aryl-2-[[[5-[(dimethylamino)methyl]-2-furanyl]methyl]thio]ethylamino analogs of ranitidine. 150 3

A prolonged type of organophosphate toxicity, previously characterized as the Intermediate Syndrome, has been recognized in 6 out of 7 prospectively studied patients poisoned by insecticide containing parathion and methyl parathion in equal proportions. The clinical characteristics included respiratory paresis, weakness in the territories of several motor cranial nerves, neck flexors and proximal limb muscles, and depressed tendon reflexes, all lasting for several days or weeks. Electromyography in the early stages disclosed diverse types of impaired neuromuscular transmission. EMG normalization preceded clinical recovery. Severe plasma butyrylcholinesterase and erythrocyte acetylcholinesterase inhibition persisted along with the occurrence of Intermediate Syndrome-related symptoms. We conclude that combined parathion and methyl parathion poisoning is more likely to induce Intermediate Syndrome than parathion poisoning alone. The mechanisms underlying this difference remain obscure. The Intermediate Syndrome shows clinical and electromyographic hallmarks of combined postsynaptic impairment of neuromuscular transmission.
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PMID:Prolonged toxicity with intermediate syndrome after combined parathion and methyl parathion poisoning. 151 8

Evidence for the involvement of Ser-203, His-447, and Glu-334 in the catalytic triad of human acetylcholinesterase was provided by substitution of these amino acids by alanine residues. Of 20 amino acid positions mutated so far in human acetylcholinesterase (AChE), these three were unique in abolishing detectable enzymatic activity (less than 0.0003 of wild type), yet allowing proper production, folding, and secretion. This is the first biochemical evidence for the involvement of a glutamate in a hydrolase triad (Schrag, J.D., Li, Y., Wu, M., and Cygler, M. (1991) Nature 351, 761-764), supporting the x-ray crystal structure data of the Torpedo californica acetylcholinesterase (Sussman, J.L., Harel, M., Frolow, F., Oefner, C., Goldman, A., Toker, L. and Silman, I. (1991) Science 253, 872-879). Attempts to convert the AChE triad into a Cys-His-Glu or Ser-His-Asp configuration by site-directed mutagenesis did not yield effective AChE activity. Another type of substitution, that of Asp-74 by Gly or Asn, generated an active enzyme with increased resistance to succinylcholine and dibucaine; thus mimicking in an AChE molecule the phenotype of the atypical butyrylcholinesterase natural variant (D70G mutation). Mutations of other carboxylic residues Glu-84, Asp-95, Asp-333, and Asp-349, all conserved among cholinesterases, did not result in detectable alteration in the recombinant AChE, although polypeptide productivity of the D95N mutant was considerably lower. In contrast, complete absence of secreted human AChE polypeptide was observed when Asp-175 or Asp-404 were substituted by Asn. These two aspartates are conserved in the entire cholinesterase/thyroglobulin family and appear to play a role in generating and/or maintaining the folded state of the polypeptide. The x-ray structure of the Torpedo acetylcholinesterase supports this assumption by revealing the participation of these residues in salt bridges between neighboring secondary structure elements.
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PMID:Mutagenesis of human acetylcholinesterase. Identification of residues involved in catalytic activity and in polypeptide folding. 151 12

Human brains fixed in 3 conventional solutions were used to compare acetylcholinesterase and butyrylcholinesterase labeling after being processed by the same histochemical procedure. The best fixative was found to be 4% paraformaldehyde in a 0.1 M phosphate buffer for 24-42 h. The addition of 2% glutaraldehyde to 2% paraformaldehyde for the same fixation time reduced the staining intensity of both enzymes. Formalin after 2 days resulted in a lighter staining intensity of fibers, senile plaques and neurofibrillary tangles, whereas after 10 days it caused the near disappearance of acetylcholinesterase-positive fibers. Finally, after more than 10 days in formalin, a certain number of senile plaques and a few neurofibrillary tangles could be observed, and those only in the case in which the substrate concentration and incubation time were increased. The fixed tissue, in either blocks or sections, can be stored for more than 1 year in a glycol solution at -17 degrees C, without the inconvenience of freezing, with good histology and histochemical preservation of both enzymes.
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PMID:Cholinesterase histochemistry in the human brain: effect of various fixation and storage conditions. 152 73

This paper examines inhibition of acetylcholinesterase (AchE) and butyrylcholinesterase (BuchE) by tetrahydroaminoacridine (THA), an acridine analog under consideration for palliative treatment of Alzheimer's dementia. THA causes linear mixed inhibition of AchE hydrolysis of acetylthiocholine, a cationic substrate (KI = 3.8 x 10(-9) M), and linear competitive inhibition of AchE hydrolysis of 7-acetoxy-4-methylcoumarin, an uncharged substrate (KI = 6.8 x 10(-9) M), and N-methyl-7-dimethylcarbamoxyquinolinium, a cationic carbamate (KI = 1.5 x 10(-8) M). Propidium association with AchE in the presence of saturating concentrations of THA is characterized by a dissociation constant of 7.7 +/- 0.7 x 10(-6) M, a value within 2-fold of the dissociation constant in the absence of THA. Association of THA with AchE is, therefore, not mutually exclusive with association of propidium at the peripheral anionic site. Moreover, THA causes dissociation of decidium complexes with AchE at concentrations compatible with a dissociation constant of 7.0 +/- 0.4 x 10(-9) M. Similar relationships were observed for THA inhibition of BuchE hydrolysis of butyrylthiocholine (KI = 2.5 x 10(-8) M) and dissociation of decidium complexes with BuchE (KD = 1.9 +/- 0.1 x 10(-8) M). These kinetic and equilibrium data uniformly indicate that THA associates with AchE and BuchE with high affinity and that the subsequent inhibition comes about through ligand association at the active center rather than at a peripheral site. The noncompetitive component of inhibition reflects association of THA with the acyl-enzyme intermediate, with subsequent effects on the rate of deacylation.
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PMID:Interaction of tetrahydroaminoacridine with acetylcholinesterase and butyrylcholinesterase. 153 17

Cholinesterases of porcine left ventricular heart muscle were characterized with respect to substrate specificity and inhibition kinetics with organophosphorus inhibitors N,N'-di-isopropyl-phosphorodiamidic fluoride (Mipafox), di-isopropylphosphorofluoridate (DFP), and diethyl p-nitro-phenyl phosphate (Paraoxon). Total myocardial choline ester hydrolysing activity (234 nmol/min/g wet wt with 1.5 mM acetylthiocholine, ASCh; 216 nmol/min/g with 30 mM butyrylthiocholine, BSCh) was irreversibly and covalently inhibited by a wide range of inhibitor concentrations and, using weighted least-squares non-linear curve fitting, residual activities as determined with four different substrates in each case were fitted to a sum of up to four exponential functions. Quality of curve fitting as assessed by the sum of squares reached its optimum on the basis of a three component model, thus, indicating the presence of three different enzymes taking part in choline ester hydrolysis. Final classification of heart muscle cholinesterases was obtained according to both substrate hydrolysis patterns with ASCh, BSCh, acetyl-beta-methylthiocholine and propionylthiocholine, and second-order rate constants for the reaction with organophosphorus inhibitors Mipafox, DFP, and Paraoxon. One choline ester-hydrolysing enzyme was identified as acetylcholinesterase (EC 3.1.1.7), and one as butyrylcholinesterase (EC 3.1.1.8). The third enzyme with relative resistance to organophosphorus inhibition was classified as atypical cholinesterase.
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PMID:Cholinesterases of heart muscle. Characterization of multiple enzymes using kinetics of irreversible organophosphorus inhibition. 154 Feb 36

The presence of acetylcholinesterase and butyrylcholinesterase was studied in chick retinal pigment epithelium. Acetylcholinesterase activity was 13 times higher than that of butyrylcholinesterase. The former showed a Km of 290 microM and a vmax of 45.4 nmol mg-1 protein min-1, while the latter showed two apparent Km values (132 microM and 666 microM). Studies on subcellular distribution revealed that both enzymes are associated with membranes. During the embryonic development butyrylcholinesterase activity decreased, while acetylcholinesterase activity increased. The possibility that these changes are related to the proliferation and differentiation processes is discussed.
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PMID:Characterization of acetylcholinesterase and butyrylcholinesterase activities in retinal chick pigment epithelium during development. 154 36

Acetylcholinesterases (EC 3.1.1.7, AChE) have varying amounts of carbohydrates attached to the core protein. Sequence analysis of the known primary structures gives evidence for several asparagine-linked carbohydrates. From the differences in molecular mass determined on sodium dodecyl sulfate-polyacrylamide gel before and after deglycosylation with N-glycosidase F (EC 3.2.2.18), it is seen that dimeric AChE from red cell membranes is more heavily glycosylated than the tetrameric brain enzyme. Furthermore, dimeric and tetrameric forms of bovine AChE are more heavily glycosylated than the corresponding human enzymes. Monoclonal antibodies 2E6, 1H11, and 2G8 raised against detergent-soluble AChE from electric organs of Torpedo nacline timilei as well as Elec-39 raised against AChE from Electrophorus electricus cross-reacted with AChE from bovine and human brain but not with AChE from erythrocytes. Treatment of the enzyme with N-glycosidase F abolished binding of monoclonal antibodies, suggesting that the epitope, or part of it, consists of N-linked carbohydrates. Analysis of N-acetylglucosamine sugars revealed the presence of N-acetylglucosamine in all forms of cholinesterases investigated, giving evidence for N-linked glycosylation. On the other hand, N-acetylgalactosamine was not found in AChE from human and bovine brain or in butyrylcholinesterase (EC 3.1.1.8) from human serum, indicating that these forms of cholinesterase did not contain O-linked carbohydrates. Despite the notion that within one species, the different forms of AChE arise from one gene by different splicing, our present results show that dimeric erythrocyte and tetrameric brain AChE must undergo different postsynthetic modifications leading to differences in their glycosylation patterns.
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PMID:Different glycosylation in acetylcholinesterases from mammalian brain and erythrocytes. 154 61


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