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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)

Human serum cholinesterase (EC 3.1.1.8) is a carbohydrate-rich glycoprotein, which reacts with 18 different lectins from plants and invertebrates by a specific precipitin reaction; most of the lectins combine with alkali-stable bound carbohydrate chains. One third of these lectin receptors appear after neuraminidase-treatment, two thirds can be demonstrated before and after removal of neuraminic acid. The specific lectin receptors of the alkali-labile carbohydrate chains are characterized and analyzed by chemical and serological methods.
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PMID:[Serum cholinesterase as a model glycoprotein (author's transl)]. 41 80

Lectins from Canavalia ensiformis, Phaseolus vulgaris, and Triticum vulgare react with arylamidase, alkaline phosphatase, gamma-glutamyltransferase, and cholinesterase of human sera by formation of enzymatically active, mostly insoluble complexes. Arylamidase, alkaline phosphatase, and cholinesterase react more intensely in sera of healthy people than in sera of patients with liver and neoplastic diseases. Arylesterase is bound to a distinct degree only by concanavalin A. The enzymes mentioned above also react slightly with the following lectins in order of decreasing intensity: Ricinus communis, Arachis hypogaea, Helix pomatia, Glycine max, Dolichos biflorus, and Ulex europaeus. Though multiple forms containing less sialic acid are favourably bound, preincubation with neuraminidase does not improve the reaction except with soybean lectin. Since higher concentrations of lectins react also with fast moving fractions of high sialic acid content, no steric hindrance of the binding between lectins and sialoenzymes is supposed, as concluded from determination of the total enzyme activity.
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PMID:[Lectins as reagents for the differentiation of serum enzymes. Lectins as reagents, I. (author's transl)]. 54 35

1. Acetylcholinesterase from human erythrocytes was solubilized with Triton X-100 in strong salt solution and partially purified by (NH(4))(2)SO(4) fractionation. This preparation showed three main bands of enzyme activity after electrophoresis on polyacrylamide gel and incubation with either alpha-naphthyl acetate or acetylthiocholine as enzyme substrate. Two of the multiple forms were completely inhibited by 10mum-eserine and one only partially. Treatment with neuraminidase had no effect on the electrophoretic pattern; therefore sialic acid does not appear to determine or affect the ratios of the acetylcholinesterase multiple forms, unlike those of the serum cholinesterase. 2. Chromatography of the preparation on Sephadex G-200 revealed one major peak of enzyme activity and a suggestion of two minor zones of mol.wt. 546000, 184000 and 93000 (i.e. in the proportion 6:2:1). The main peak was almost completely separated from the Triton X-100 and the overall purification was about 600-fold. Further attempts to purify the enzyme by absorption on calcium phosphate gels were unsuccessful. 3. Electrophoresis of the enzyme preparation on a polyacrylamide gradient for 24h revealed three main bands that corresponded to the three values for molecular weights obtained by column chromatography. After 70h of electrophoresis a further three zones of activity developed making six molecular entities, the molecular weights of which were simple multiples of a monomer, thus resembling the cholinesterase found in serum.
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PMID:Multiple forms of acetylcholinesterase from human erythrocytes. 473 38

L-Carnitine (L-C) is involved in the transport of acyl groups into mitochondria for beta-oxidation, although its role in the adult brain is still uncertain. We have shown before that the uptake of L-carnitine into cultured rat cortical neurones was dependent on temperature as well as the Na gradient and is inhibited by compounds resembling its structure, like gamma-aminobutyric acid (GABA), but most potently by specific GABA uptake blockers. In this study we have characterised this uptake process further. We have shown that the uptake of L-carnitine may be dependent on Cl ions, in addition to Na ions, but non on Ca ions. The L-C uptake was inhibited by substituent anions in the order gluconate (83%) > isethionate (32%), with propionate being ineffective, whereas GABA uptake was inhibited most potently by propionate substitution (79%) and equally by isethionate and gluconate (67%). This L-C uptake process was not affected by the amino acids, glutamine or lysine, up to 1 mM concentration, although beta-alanine at 500 microM caused a 38% inhibition. The uptake of L-C was also significantly inhibited by structurally-related compounds, with a carbon chain length of three to six atoms, possessing an amine group and/or a carboxyl group. At a concentration of 500 microM, 3-aminopropane sulphonic acid (53%), gamma-butyrobetaine (31%), gamma-hydroxybutyric acid (34%) and 4 methylaminobutyric acid (33%). Other compounds were effective only at the lower concentration of 10 microM, such as butyric acid (25%), nicotinic acid (26%), isonicotinic acid (26%), hexanoic acid (23%) and at 100 microM, like 6-aminocapric acid (22%). Drugs suggested to affect membrane properties, such as chlorpromazine, was without effect at 1 or 10 microM, whereas flunarizine (FLU) at 1 microM inhibited both L-C (24%) and GABA uptake (17%). Other drugs like the cholinesterase inhibitors, tacrine and eserine, also had a small inhibitory effect on L-C uptake, reducing it at 1 microM by 22 and 21% respectively, although higher concentrations were toxic (> 100 microM). Pretreatment of the cells with neuraminidase (50 U ml-1, 10 min) reduced the subsequent uptake of both L-C (18%) and GABA (42%). Hypoxia (3 h) also significantly attenuated L-C uptake (42%), however part of these effects were related to the loss of cell viability. In summary, L-C uptake occurs by a complex mechanism which at least in part may occur by a Na/Cl cotransport mechanism, which could be similar, to that of GABA or may even in part occur via the GABA transporter.
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PMID:Structural, metabolic and ionic requirements for the uptake of L-carnitine by primary rat cortical cells. 881 42

To understand the role of glycosylation in the circulation of cholinesterases, we compared the mean residence time of five tissue-derived and two recombinant cholinesterases (injected intravenously in mice) with their oligosaccharide profiles. Monosaccharide composition analysis revealed differences in the total carbohydrate, galactose, and sialic acid contents. The molar ratio of sialic acid to galactose residues on tetrameric human serum butyrylcholinesterase, recombinant human butyrylcholinesterase, and recombinant mouse acetylcholinesterase was found to be approximately 1.0. For Torpedo californica acetylcholinesterase, monomeric and tetrameric fetal bovine serum acetylcholinesterase, and equine serum butyrylcholinesterase, this ratio was approximately 0.5. However, the circulatory stability of cholinesterases could not be correlated with the sialic acid-to-galactose ratio. Fractionation of the total pool of oligosaccharides obtained after neuraminidase digestion revealed one major oligosaccharide for human serum butyrylcholinesterase and three or four major oligosaccharides in other cholinesterases. The glycans of tetrameric forms of plasma cholinesterases (human serum butyrylcholinesterase, fetal bovine serum acetylcholinesterase, and equine serum butyrylcholinesterase) clearly demonstrated a reduced heterogeneity and higher maturity compared with glycans of monomeric fetal bovine serum acetylcholinesterase, dimeric tissue-derived T. californica acetylcholinesterase, and recombinant cholinesterases. T. californica acetylcholinesterase, recombinant cholinesterases, and monomeric fetal bovine serum acetylcholinesterase showed a distinctive shorter mean residence time (44-304 min) compared with tetrameric forms of plasma cholinesterases (1902-3206 min). Differences in the pharmacokinetic parameters of cholinesterases seem to be due to the combined effect of the molecular weight and charge- and size-based heterogeneity in glycans.
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PMID:Role of oligosaccharides in the pharmacokinetics of tissue-derived and genetically engineered cholinesterases. 944 38

It had been proposed that sialyl-residues on the surface of the cell control the activity of certain plasma membrane ecto-enzymes. We have tested the effects of several established (or presumptive) ecto-enzymes in tissue cultures of CNS-derived cells. Application of neuraminidases to cultured mouse neuroblastoma (N-18), neonatal Syrian hamster astrocytes (NN), human astrocytoma (Cox clone) and two lines of primary mouse astroblasts failed to change the activity of ecto-ATPase and 5'-nucleotidase. Only two of the seven neuraminidase preparations produced marked or moderate increases in inorganic pyrophosphatase, p-nitrophenylphosphatase and cholinesterase. We have concluded that the stimulation of these enzymes was not due to removal of sialyl-residues. We suggest that contaminants (haemolysins?) in neuraminidase preparations of Clostridium perfringens increased membrane permeability and facilitated substrate-product translocation.
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PMID:On the activation of plasma membrane ecto-enzymes by treatment with neuraminidase. 1217 May 85