Multiple binding sites involved in the effect of choline esters on decarbamoylation of monomethylcarbamoyl- or dimethylcarbamoly-acetylcholinesterase
| Autor: | Seung-Hee Cha, Chang-Hee Jung, Yun-Bae Kim, Dai-Eun Sok, Seung-Ju Choi |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
Steric effects
Stereochemistry Binding Competitive Biochemistry Choline Mice chemistry.chemical_compound Acetylcholine binding Non-competitive inhibition medicine Animals Binding site Molecular Biology Binding Sites biology Osmolar Concentration Brain Active site Esters Cell Biology Hydrogen-Ion Concentration Acetylcholinesterase Acetylcholine Kinetics Acetylthiocholine chemistry biology.protein Carbamates Acyl group Research Article medicine.drug |
| Zdroj: | Biochemical Journal. 301:713-720 |
| ISSN: | 1470-8728 0264-6021 |
| DOI: | 10.1042/bj3010713 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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