The acyl-group specificity of choline acetylase

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Abstract
The acyl-group specificity of crude and purified brain choline-acetylase preparations from pigeon, sheep and rat has been studied. The preparations were coupled to a pigeon-liver activating system as a source of acyl-coenzyme A derivatives. In preliminary experiments, the activation spectrum of extracts of liver and brain and the optimum conditions for activation were studied in order to ensure that the formation of acyl-coenzyme A derivatives was not a rate-limiting step. The rate of activation by liver extracts increased with increasing chain length, but the reverse was true of brain. Cysteine, used by previous workers as a component of the choline-acetylase system, was found to act as an acyl-group acceptor and was replaced by boro-hydride. Crude brain preparations were able to synthesize all the choline esters from acetate to hexanoate and also palmitoylcholine. Purification studies showed that 3 enzymes were involved. Palmitoylcholine synthesis was studied in brain and in liver. It required coenzyme A and adenosine triphosphate as well as palmitate and choline, and the 2-stage nature of the synthesis was demonstrated. Palmitoylcholine hydrolysis was catalyzed by an enzyme in tissues which was distant from known cholinesterases.