Author/Editor		Goličnik, Marko; Stojan, Jure
Title		Transient kinetic approach to the study of acetylcholinesterase reversible inhibition by eseroline
Type		članek
Source		J Enzym Inhib
Vol. and No.		Letnik 17, št. 5
Publication year		2002
Volume		str. 279-85
Language		eng
Abstract		The kinetic rate constants for interaction of (- )-eseroline-(3aS-cis)-1,2,3,3a,8,8a-hexahydro-1,3a,8-trimethylpy rrolo-[2,3-b]indol-5-01 with electric eel acetylcholinesterase (EC 3.1.1.7, acetylcholine acetylhydrolase) were measured at a low substrate concentration according to a transient kinetic approach by using a rapid experimental technique. The measurements were carried out on a stopped-flow apparatus where pre-incubated samples of enzyme with various inhibitor concentrations were diluted with a buffer solution containing the substrate. T'he experimental data in the form of sigmoidshaped progress curves were analysed by applying an explicit progress curve equation that described the time dependence of product released during the reaction. The kinetic parameters were evaluated by non-linear regression treatment and the values of the corresponding constants showed approximately the equal affinities of eseroline and eserine (cf. Stojan, J. and Zorko, M. (1997) Biochim. Biophys. Acta,1337, 75-84.) for binding into the active centre of the enzyme. On the other hand, the kinetic rates for association and dissociation of eseroline were two grades of magnitude higher than those of eserine. The explanation appears to be a substantionally impaired gliding of eserine into the active site gorge by the great mobility of the carbamoyl tail as well as by its numerous possible interactions with the residues lining the gorge. Additionally, a study of the dependence of the transition phase information on the inhibitor concentration was carried out using our experimental data.
Descriptors		ACETYLCHOLINESTERASE KINETICS CHOLINESTERASE INHIBITORS PHYSOSTIGMINE BINDING SITES ELECTROPHORUS ACETYLCHOLINE SPECTROPHOTOMETRY