Philip Barnett and Terrone L. Rosenberry.
Inactivation of Electrophorous Electricus Acetylcholinesterase by Benzenemethane Sulfonylfluoride.
Archives of Biochemistry and Biophysics 190:202-205, (1978).
ABSTRACT
Benzenemethanesulfonyl fluoride (329-98-6) is an irreversible inactivator of many esterases including mammalian acetylcholinesterases. However previous reports indicated that acetylcholinesterase from the electric eel Electrophorus electricus (EC 3.1.1.7) failed to react with benzenemethane sulfonylfluoride at measurable rates. We report here that eel acetylcholinesterase reacts with this inactivator at a low rate. Hydrolysis of the sulfonylating agent was so much faster than enzyme inactivation that, under most conditions, there appeared to be only slight inactivation. Like the reaction of other active site acylating agents with this enzyme, inactivation can be accelerated in the presence of certain organic cations. We introduce a rate equation for enzyme sulfonylation which incorporates both the hydrolysis of the inactivator and the complication that fluoride resulting from hydrolysis of the inactivator is a potent competitive inhibitor of this enzyme. This rate equation accurately described the time course of enzyme inactivation.