Author/Editor     Stojan, Jure; Brochier, Laure; Alies, Carole; Colletier, Jacques Philippe; Fournier, Didier
Title     Inhibition of Drosophila melanogaster acetylcholinesterase by high concentations of substrate
Type     članek
Source     Eur J Biochem
Vol. and No.     Letnik 271
Publication year     2004
Volume     str. 1364-71
Language     eng
Abstract     Acetylcholine hydrolysis by acetylcholinesterase is inhibited at high substrate concentrations. To determine the residues involved in this phenomenon, we have mutated most of the residues lining the active-site gorge but mutating these did not completely eliminate hydrolysis. Thus, we analyzed the effect of a nonhydrolysable substrate analogue on substrate hydrolysis and on reactivation of an analogue of the acetylenzyme. Analyses of various models led us to propose the following sequence of events: the substrate initially binds at the rim of the active-site gorge and then slides down to the bottom of the gorge where it is hydrolyzed. Another substrate molecule can bind to the peripheral site: (a) when the choline is still inside the gorge - it will thereby hinder its exit; (b) after choline has dissociated but before deacetylation occurs - binding at the peripheral site increases deacetylation rate but (c) if a substrate molecule bound to the peripheral site slides down to the bottom of the active-site before the catalytic serine is deacetylated, its new position will prevent the approach of water, thus blocking deacetylation.
Descriptors     DROSOPHILA MELANOGASTER
ACETYLCHOLINESTERASE
BINDING SITES
ACETYLCHOLINE
KINETICS
ACETYLTHIOCHOLINE
MUTAGENESIS, SITE-DIRECTED
HYDROLYSIS
SUBSTRATE SPECIFICITY