Accession Number : ADA328625

Title :   Direct Kinetic Evidence for the Formation of an Acylpyridinium Intermediate in Synthetic p-Nitrophenyl Esterase-Catalyzed Hydrolysis Reactions.

Descriptive Note : Technical rept.,

Corporate Author : INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS DEPT OF CHEMISTRY

Personal Author(s) : Wang, Guang-Jia ; Fife, Wilmer K.

PDF Url : ADA328625

Report Date : 1996

Pagination or Media Count : 27

Abstract : The kinetics of the hydrolysis of p-nitrophenyl alkanoates 2 catalyzed by 1 were investigated in aqueous Tris buffer solution. Direct evidence for the existence of an N- acylpyridinium intermediate 3 was obtained for 1-catalyzed hydrolysis of 2 (n=2-10). Increase of the alkyl chain length leads to an increase in the acylation rate which reaches a maximum for 2 (n=6). The acylation rate then decreases progressively with further increases of alkyl chain length in substrate esters. The deacylation rate was also found to exhibit a maximum for the same substrate 2 (n=6). These results are similar to those previously reported with cholesterol esterase as catalyst for the same hydrolysis reaction. The acylation reaction is first-order in catalyst concentration and exhibits saturation kinetics at high substrate concentration in accordance with the Michaelis-Menten model for enzyme reaction kinetics.

Descriptors :   *REACTION KINETICS, *HYDROLYSIS, *ACYLATION, SUBSTRATES, SATURATION, LENGTH, CATALYSTS, ESTERS, ALKYL RADICALS, BUFFERS(CHEMISTRY), ENZYME CHEMISTRY.

Subject Categories : Organic Chemistry
      Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE