title: Inhibition of Drosophila melanogaster acetylcholinesterase by high concentrations of substrate.
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.
authors.affiliation: Institute of Biochemistry, Medical Faculty, University of Ljubljana, Slovenia.
authors.forename: Jure
authors.initials: J
authors.lastname: Stojan
authors.forename: Laure
authors.initials: L
authors.lastname: Brochier
authors.forename: Carole
authors.initials: C
authors.lastname: Alies
authors.forename: Jacques Philippe
authors.initials: JP
authors.lastname: Colletier
authors.forename: Didier
authors.initials: D
authors.lastname: Fournier
mesh_terms: D000110:Acetylcholinesterase / Q000737:chemistry*; D000818:Animals; D001665:Binding Sites; D001671:Biochemistry / Q000379:methods*; D020134:Catalytic Domain; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004331:Drosophila melanogaster / Q000201:enzymology*; D006868:Hydrolysis; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D002800:Cholinesterase Inhibitors; D018076:DNA, Complementary; D000110:Acetylcholinesterase