Accession Number : AD0706422

Title :   THE KINETICS OF THE REACTION OF N,N-DIMETHYL-2-PHENYLAZIRIDINIUM ION WITH BOVINE ERYTHROCYTE ACETYLCHOLINESTERASE,

Corporate Author : DEFENCE RESEARCH ESTABLISHMENT OTTAWA (ONTARIO)

Personal Author(s) : Purdie,Jocelyn E. ; Heggie,R. M.

Report Date : 22 AUG 1969

Pagination or Media Count : 8

Abstract : The kinetics of the hydrolysis of N,N-dimethyl-2-phenylaziridinium ion (DPA) have been studied over the pH range 5.5-8.0 as have the kinetics of the interaction of DPA with bovine erythrocyte acetylcholinesterase. The enzyme is initially inhibited reversibly and subsequently irreversibly towards acetylcholine hydrolysis. Between pH values of 6.0 and 8.0 the kinetics of the irreversible inhibition are consistent with either of two kinetically indistinguishable mechanisms, one involving transformation of the initial reversible complex and the other an independent attack on the uncomplexed enzyme. The first mechanism gives rise to a first-order rate constant which is comparable with that for the hydrolysis of DPA but which increases with decreasing pH; an acidic group on the enzyme with pK(a) between 6.0 and 7.0 may be involved. The second-order rate constant arising from the second treatment goes through a maximum at pH 7.3. At pH 5.5 the kinetics are not consistent with either mechanism. (Author)

Descriptors :   (*ACETYLCHOLINESTERASE, CHEMICAL REACTIONS), REACTION KINETICS, HYDROLYSIS, NITROGEN HETEROCYCLIC COMPOUNDS, PH FACTOR, CANADA

Subject Categories : Biochemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE