Kinetic studies of the choline acetyltransferase reaction using isotope exchange at equilibrium.

Isotope exchange at equilibrium has been used to study the kinetic mechanism of the choline acetyltransferase reaction. The choline-acetylcholine, acetyl-CoA-acetylcholine, and CoA-acetyl-CoA exchange patterns are qualitatively consistent with a Theorell-Chance mechanism. However, quantitative differences are observed when the experimental results are compared to theoretical fits of the data for a Theorell-Chance mechanism. It is concluded that the kinetic mechanism of the choline acetyltransferase reaction can best be described as a random Theorell-Chance mechanism in which a low but finite amount of ternary complex exists.