A radiochemical method for the estimation of choline acetyltransferase

1. A radiochemical method for the estimation of choline acetyltransferase (choline acetylase) has been devised which involves the formation of labelled acetylcholine from labelled acetate. 2. 1-(14)C]Acetate and coenzyme A are pre-incubated in the presence of non-rate-limiting concentrations of acetyl-coenzyme A synthetase to give 1-(14)C]acetyl-coenzyme A, which then reacts with choline in the presence of the acetyltransferase to give (14)C]acetylcholine. 3. Any (14)C]-acetyl-coenzyme A remaining at the end of the reaction is destroyed by the addition of excess of hydroxylamine, and (14)C]acetylcholine is freed from other labelled compounds by precipitation with sodium tetraphenylborate (Kalignost). 4. The washed precipitate is dissolved in acetonitrile-benzyl alcohol and estimated by scintillation counting. 5. Advantages over other methods are discussed.