Horse serum butyrylcholinesterase kinetics: a molecular mechanism based on inhibition studies with dansylaminoethyltrimethylammonium.
The kinetics of the hydrolysis of butyrylthiocholine by horse serum butyrylcholinesterase (acylcholine acylhydrolase; BuChE; EC 3.1.1.8) exhibit an activation phenomenon at high substrate concentrations. At least two mechanistic models can account for the enzyme kinetics: one assumes the binding of an additional substrate molecule on the acyl-enzyme intermediate, and the other hypothesizes the existence of a peripheral regulatory site for the substrate. (1-Dimethylaminonaphthalene-5-sulfonamidoethyl)-trimethylammonium perchlorate, a potent reversible inhibitor, appears to affect BuChE activity by binding to a peripheral site. The inhibition is of the mixed type at low substrate concentrations and of the competitive type at high substrate concentrations. This is consistent with a peripheral site for the binding of the substrate responsible for the activation phenomenon.
Cauet
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G
Laboratoire de Technologie Enzymatique, Université de Technologie de Compiègne, France.
Friboulet
A
A
Thomas
D
D
D000818:Animals; D002091:Butyrylcholinesterase / Q000097:blood* / Q000302:isolation & purification; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D002802:Cholinesterases / Q000097:blood*; D006736:Horses / Q000097:blood*; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D011485:Protein Binding; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*
D002800:Cholinesterase Inhibitors; D000644:Quaternary Ammonium Compounds; C012951:DNS-chol; D002091:Butyrylcholinesterase; D002802:Cholinesterases