Document Detail

Model for "charge-relay": acceleration by carboxylate anion in intramolecular general base-catalyzed ester hydrolysis by the imidazolyl group.
MedLine Citation:
PMID:  19738     Owner:  NLM     Status:  MEDLINE    
The effect of benzoate anion on intramolecular general base-catalyzed ester hydrolysis by the imidazolyl group in endo-5-[4'(5')-imidazolyl]bicyclo[2.2.1]hept-endo-2-yl trans-cinnamate was examined in dioxane/H(2)O solutions. Benzoate anion exhibited a remarkable acceleration of the intramolecular general base-catalyzed hydrolysis of endo-5-[4'(5')-imidazolyl]bicyclo[2.2.1]hept-endo-2-yl trans-cinnamate by the imidazolyl group. The rate of hydrolysis in the presence of the benzoate anion increased with the dioxane mole fraction and was proportional to the concentration of benzoate anion. On the other hand, the rate of hydrolysis of endo-5-[4'(5')-imidazolyl]bicyclo[2.2.1]hept-endo-2-yl trans-cinnamate in the absence of benzoate anion decreased with the dioxane mole fraction. Thus, the ratio of the rate in the presence of benzoate anion to that in the absence of benzoate anion drastically increased with the dioxane mole fraction and attained a 2500-fold rate acceleration at a dioxane mole fraction of 0.42 (the highest experimentally attainable) when the concentration of benzoate anion was 0.5 M. The proposed mechanism involves proton abstraction by the benzoate anion from the imidazolyl group, followed by proton abstraction by the imidazolyl group from H(2)O, resulting in effective general base-catalysis of hydrolysis. The results of the present paper provide support for the "charge-relay" system in serine proteases.
M Komiyama; M L Bender; M Utaka; A Takeda
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  74     ISSN:  0027-8424     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  1977 Jul 
Date Detail:
Created Date:  1977-10-14     Completed Date:  1977-10-14     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  2634-8     Citation Subset:  IM    
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MeSH Terms
Hydrogen-Ion Concentration
Models, Chemical
Peptide Hydrolases / metabolism
Reg. No./Substance:
0/Benzoates; 0/Dioxanes; 0/Imidazoles; EC 3.4.-/Peptide Hydrolases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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