scholarly journals Potentiation effect of choline esters on choline-catalysed decarbamoylation of dimethylcarbamoyl-acetylcholinesterase

1992 ◽  
Vol 284 (1) ◽  
pp. 153-160 ◽  
Author(s):  
Y B Kim ◽  
C H Jung ◽  
S J Choi ◽  
W J Seo ◽  
S H Cha ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Quaternary Ammonium ◽  
Acyl Chain ◽  
Requirement Analysis ◽  
Ester Bond ◽  
Choline Ester ◽  
Anionic Sites ◽  
Structural Requirement ◽  
Potentiation Effect ◽  
Choline Esters

The choline esters potentiated the choline-catalysed decarbamoylation of dimethylcarbamoyl-acetylcholinesterase in proportion to the length of acyl group, although esters containing an acyl chain longer than the hexanoyl group exhibited a corresponding decrease in the potentiation. In structural requirement analysis it was found that both the quaternary ammonium moiety and the ester bond were important for the effective acceleration of choline-catalysed decarbamoylation. In general, the respective thiocholine ester was found to be more effective than the corresponding choline ester. Whereas the binding affinity (Ka) of choline in the decarbamoylation was not significantly altered, the maximum decarbamoylation rate (kr(max.)) of choline was greatly enhanced in the presence of choline esters or thiocholine esters. Along with the above observation, the isotope solvent effect, the effect of ionic strength and the antagonism studies demonstrate that the choline esters or thiocholine esters may interact with one of peripheral anionic sites, and thereby make the choline-catalysed decarbamoylation more favourable.

scholarly journals Multiple binding sites involved in the effect of choline esters on decarbamoylation of monomethylcarbamoyl- or dimethylcarbamoly-acetylcholinesterase

1994 ◽  
Vol 301 (3) ◽  
pp. 713-720 ◽  
Author(s):  
D E Sok ◽  
Y B Kim ◽  
S J Choi ◽  
C H Jung ◽  
S H Cha
Keyword(s):  
Active Site ◽  
Binding Sites ◽  
Inhibitory Action ◽  
Competitive Inhibition ◽  
Acyl Chain ◽  
Active Centre ◽  
Multiple Binding Sites ◽  
Wide Range ◽  
Choline Esters ◽  
Multiple Binding

Multiple binding sites for inhibitory choline esters in spontaneous decarbamoylation of dimethylcarbamoyl-acetylcholinesterase (AChE) were suggested from a wide range of IC50 values, in contrast with a limited range of AC50 values (concentration giving 50% of maximal activation) at a peripheral activatory site. Association of choline esters containing a long acyl chain (C7-C12) with the hydrophobic zone in the active site could be deduced from a linear relationship between the size of the acyl group and the inhibitory potency in either spontaneous decarbamoylation or acetylthiocholine hydrolysis. Direct support for laurylcholine binding to the active site might come from the competitive inhibition (Ki 33 microM) of choline-catalysed decarbamoylation by laurylcholine. Moreover, its inhibitory action was greater for monomethylcarbamoyl-AChE than for dimethylcarbamoyl-AChE, where there is a greater steric hindrance at the active centre. In further support, the inhibition of pentanoylthiocholine-induced decarbamoylation by laurylcholine was suggested to be due to laurylcholine binding to a central site rather than a peripheral site, similar to the inhibition of spontaneous decarbamoylation by laurylcholine. Supportive data for acetylcholine binding to the active site are provided by the results that acetylcholine is a competitive inhibitor (Ki 7.6 mM) of choline-catalysed decarbamoylation, and its inhibitory action was greater for monomethylcarbamoyl-AChE than for dimethylcarbamoyl-AChE. Meanwhile, choline esters with an acyl group of an intermediate size (C4-C6), more subject to steric exclusion at the active centre, and less associable with the hydrophobic zone, appear to bind preferentially to a peripheral activity site. Thus the multiple effects of choline esters may be governed by hydrophobicity and/or a steric effect exerted by the acyl moiety at the binding sites.

CHANGES IN THE ELECTROCARDIOGRAM AND HEART CHOLINE ESTER CONTENT OF THIAMINE-DEFICIENT AND PAIR-FED RATS

1956 ◽  
Vol 34 (1) ◽  
pp. 845-859
Author(s):  
A. B. L. Beznák
Keyword(s):  
Paper Chromatography ◽  
Filter Paper ◽  
Trichloroacetic Acid ◽  
Frog Heart ◽  
Choline Ester ◽  
Normal Pair ◽  
Acetyl Choline ◽  
Ester Content ◽  
Rat Hearts ◽  
Choline Esters

The choline ester content of trichloroacetic acid extracts of thiamine-deficient, pair-fed, and normal rat hearts was determined by differential assays on the eserinized frog rectus and guinea pig gut. The thiamine-deficient hearts contained about 3.5 times more choline ester than the normal hearts, while the pair-fed ones about twice as much. It is concluded from results of differential assays and filter paper chromatography of the trichloroacetic acid extracts that the chief, probably the only, choline ester in all the three groups is acetyl choline. It is also pointed out that the possibility of the presence of a mixture of pyruvyl, propionyl, and acetyl choline in the thiamine-deficient heart could not be excluded with these methods. Bradycardia and increased R voltage develop both in thiamine-deficient and in pair-fed rats, but are more pronounced in the former group. When the three groups of rats, normal, pair-fed, and thiamine-deficient, were treated as a single population a positive correlation was found between R voltage and total ACh equivalent and an inverse correlation between heart rate and ACh equivalent. The trichloroacetic acid extracts of rat hearts of all the three groups contain a positive inotropic substance (or substances) and substances which absorb ultraviolet light, most probably nucleic acid derivatives, which interfere with the frog heart assay of choline esters. The ultraviolet absorbing compounds are the bearers of most of the positive inotropic activity. These can be separated from the negative inotropic choline esters by filter paper chromatography.

scholarly journals Isolation of choline esters from aqueous solutions by extraction with sodium tetraphenylboron in organic solvents

1969 ◽  
Vol 113 (2) ◽  
pp. 291-298 ◽  
Author(s):  
F. Fonnum
Keyword(s):  
Cation Exchange ◽  
Organic Solvents ◽  
Extraction Procedure ◽  
Choline Ester ◽  
Anion Exchange Resins ◽  
Choline Esters ◽  
Group 3 ◽  
Two Phases ◽  
Sodium Tetraphenylboron ◽  
Exchange Resins

1. The method is based on the observation that choline esters and sodium tetraphenylboron (Kalignost) form complexes that are insoluble in water but soluble in organic solvents such as nitriles, higher ketones and benzyl alcohol. 2. The extraction procedure is an example of liquid cation exchange where tetraphenylboron is the cation-exchange group. 3. The proportion of choline esters extracted depends on the type and total amount of cation in the aqueous phase and the amount of sodium tetraphenylboron in the organic solvent. 4. The proportion of choline esters extracted is independent of the choline ester concentration, the pH (between 8 and 3) and the relative volumes of the two phases. 5. The affinity of sodium tetraphenylboron for choline esters increases with an increase in the size of the acyl group. 6. The choline ester extracted can be released into an aqueous solution by treatment with strong acids, silver salts and anion-exchange resins.

Phosphonic acid analogues of carbohydrate metabolites. Dihydroxypropylphosphonic acid. II. Substrate specificity of L-glycerol-3-phosphate : NAD oxidoreductase

1969 ◽  
Vol 47 (10) ◽  
pp. 992-994 ◽  
Author(s):  
Erich Baer ◽  
Darius J. Nazir ◽  
Hemendra Basu
Keyword(s):  
Enzyme Activity ◽  
Substrate Specificity ◽  
Phosphonic Acid ◽  
Inhibitory Effect ◽  
Phosphate Ester ◽  
Ester Bond ◽  
Structural Requirement ◽  
Nad Oxidoreductase ◽  
Carbohydrate Metabolites

The specificity of L-glycerol-3-phosphate : NAD oxidoreductase with regard to the phosphate ester bond of L-α-glycerophosphoric acid was investigated by means of L- and DL-dihydroxypropylphosphonic acid. The phosphate ester bond was found to be an essential structural requirement for enzyme activity. Neither L- nor DL-dihydroxypropylphosphonic acid has an inhibitory effect on the oxidation of L-α-glycerophosphoric acid by L-glycerol-3-phosphate : NAD oxidoreductase.

scholarly journals Anionic sites in the glomerular basement membrane. In vivo and in vitro localization to the laminae rarae by cationic probes.

1979 ◽  
Vol 81 (1) ◽  
pp. 137-153 ◽  
Author(s):  
Y S Kanwar ◽  
M G Farquhar
Keyword(s):  
Ionic Strength ◽  
Basement Membrane ◽  
Glomerular Basement Membrane ◽  
Left Kidney ◽  
High Ionic Strength ◽  
Basement Membranes ◽  
Mesangial Matrix ◽  
Anionic Sites

Cationized ferritin (CF) of narrow pI range (7.3-7.5) and the basic dye ruthenium red (RR) have been used as cationic probes to partially characterize anionic sites previously demonstrated in the glomerular basement membrane (GBM). When CF was given i.v. to normal rats and the left kidney was fixed by perfusion 15 min thereafter, clusters of CF molecules were found throughout the lamina rara interna (LRI), lamina rara externa (LRE), and mesangial matrix distributed at regular (approximately 60 nm) intervals. When kidneys were perfused with aldehyde fixative containing RR, small (20 nm) RR-stained particles were seen in the same locations distributed with the same 60 nm repeating pattern, forming a quasiregular, lattice-like arrangement. Fine (approximately 3 nm) filaments connected the sites and extended between them and the membranes of adjoining endothelial and epithelial cells. When CF was given i.v. followed by perfusion with RR in situ, both probes localized to the same sites. CF remained firmly bound after prolonged perfusion with 0.1-0.2 M KCl or NaCl. It was displaced by perfusion with buffers of high ionic strength (0.4-0.5 M KCl) or pH (less than 3.0 or greater than 10.0). CF also bound (clustered at approximately 60 nm intervals) to isolated GBM's, and binding was lost when such isolated GBM's were treated with buffers of high ionic strength or pH. These experiments demonstrate the existence of a quasi-regular, lattice-like network of anionic sites in the LRI and LRE and the mesangial matrix. The sites are demonstrable in vivo (by CF binding), in fixed kidneys (by RR staining), and in isolated GBM's (by CF binding). The results obtained with CF show that the binding of CF (and probably also RR) to the laminae rarae is electrostatic in nature since it is displaced by treatment with buffers of high ionic strength or pH. With RR the sites resemble in morphology and staining properties the proteoglycan particles found in connective tissue matrices and in association with basement membranes in several other locations.

Choline esters in the marine gastropods Nucella emarginata and Acanthina spirata: A new choline ester, tentatively identified as N-methylmurexine

1974 ◽  
Vol 5 (3-4) ◽  
pp. 191-198 ◽  
Author(s):  
Jeanne A. Bender ◽  
Kathryn DeRiemer ◽  
Thomas E. Roberts ◽  
Robert Rushton ◽  
Paul Boothe ◽  
...  
Keyword(s):  
Choline Ester ◽  
Marine Gastropods ◽  
Choline Esters ◽  
Nucella Emarginata

CHANGES IN THE ELECTROCARDIOGRAM AND HEART CHOLINE ESTER CONTENT OF THIAMINE-DEFICIENT AND PAIR-FED RATS

1956 ◽  
Vol 34 (5) ◽  
pp. 845-859 ◽  
Author(s):  
A. B. L. Beznák
Keyword(s):  
Paper Chromatography ◽  
Filter Paper ◽  
Trichloroacetic Acid ◽  
Frog Heart ◽  
Choline Ester ◽  
Normal Pair ◽  
Acetyl Choline ◽  
Ester Content ◽  
Rat Hearts ◽  
Choline Esters

The choline ester content of trichloroacetic acid extracts of thiamine-deficient, pair-fed, and normal rat hearts was determined by differential assays on the eserinized frog rectus and guinea pig gut. The thiamine-deficient hearts contained about 3.5 times more choline ester than the normal hearts, while the pair-fed ones about twice as much. It is concluded from results of differential assays and filter paper chromatography of the trichloroacetic acid extracts that the chief, probably the only, choline ester in all the three groups is acetyl choline. It is also pointed out that the possibility of the presence of a mixture of pyruvyl, propionyl, and acetyl choline in the thiamine-deficient heart could not be excluded with these methods. Bradycardia and increased R voltage develop both in thiamine-deficient and in pair-fed rats, but are more pronounced in the former group. When the three groups of rats, normal, pair-fed, and thiamine-deficient, were treated as a single population a positive correlation was found between R voltage and total ACh equivalent and an inverse correlation between heart rate and ACh equivalent. The trichloroacetic acid extracts of rat hearts of all the three groups contain a positive inotropic substance (or substances) and substances which absorb ultraviolet light, most probably nucleic acid derivatives, which interfere with the frog heart assay of choline esters. The ultraviolet absorbing compounds are the bearers of most of the positive inotropic activity. These can be separated from the negative inotropic choline esters by filter paper chromatography.

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