Avtor/Urednik		Marcel, Veronique; Estrada-Mondaca, Sandino; Magne, Frederic; Stojan, Jure; Klaebe, Alain; Fournier, Didier
Naslov		Exploration of the Drosophila acetylcholinesterase substrate activation site using a reversible inhibitor (Triton X-100) and mutated enzymes
Tip		članek
Vir		J Biol Chem
Vol. in št.		Letnik 275, št. 16
Leto izdaje		2000
Obseg		str. 11603-9
Jezik		eng
Abstrakt		Cholinesterases are activated at low substrate concentration, and this is followed by inhibition as the level of substrate increases. However, one of these two components is sometimes lacking. In Drosophila acetylcholinesterase, the two phases are present, allowing both phenomena to be studied. Several kineti schemes can explain this complex kinetic behavior. Among them, one model assumes that activation results from the binding of a substrate molecule to a non-productive site affecting the entrance of a substrate molecule into the active site. To test this hypothesis, we looked for an inhibitor competitive for activation and we found Triton X-100. Using organophosphates or carbamates as hemisubstrates, we showed that Triton X-100 inhibits or increases phosphorylation or carbamoylation of the enzyme. In vitro mutagenesis of the residues lining the active site gorge allowed us to locate the Triton X-100 binding site at the rim of the gorge with glutamate 107 playing the major role. These results led to the hypothesis that substrate binding at this site affects the entrance of another substrate molecule into the active site cleft.
Deskriptorji		ACETYLCHOLINESTERASE OCTOXYNOL BINDING SITES DROSOPHILA MELANOGASTER GLUTAMIC ACID HYDROLYSIS MODELS, CHEMICAL MUTAGENESIS, SITE-DIRECTED PHOSPHORYLATION PROTEIN CONFORMATION