Studies on the Kinetic Mechanism and Salt Activation of Bovine Brain Choline Acetyltransferase

Abstract: :The kinetic mechanism of bovine brain choline acetyltransferase has been studied using acetylaminocholine as a dead‐end inhibitor and di‐methylaminoethanol as an alternate substrate. Acetylaminocholine inhibition is competitive with respect to acetylcholine and noncompetitive with respect to choline. Dimethylaminoethanol exhibits one‐sixth the Vmax obtained with choline. These results suggest that the reaction obeys a sequential random kinetic mechanism. Salt activation of the enzyme is nonspecific with respect to monovalent anions, and results in a parallel increase in the Km for choline and the Ki for acetylcholine. These results support the conclusion that salt activation of choline acetyltransferase is a nonspecific effect and that no specific chloride ion regulation of this enzyme occurs in vivo.