Serum cholinesterase inhibition by boronic acids.

Horse serum cholinesterase (acylcholine acylhydrolase, EC 3.1.1.8) was reversibly inhibited by a variety of alkyl- and areneboronic acids with Ki values ranging from 6.2 mM (methaneboronic acid) to 3.1 microM (diphenylboric acid). Binding to the enzyme was apparently at the active center, because inhibition obeyed competitive kinetics and because boronic acids protected the enzyme from inactivation by phenylmethanesulfonyl fluoride. Boronic acids should prove useful in probing the active center of serum cholinesterase.