The drug Botox (botulinum toxin) is derived from a toxin produced by the bacterial species Clostridium botulinum. It is often used for cosmetic purposes to tighten skin and reduce the appearance of facial wrinkles. The toxin is an inhibitor of the enzyme acetylcholinesterase (AChase).
Which of the following processes is the botulinum toxin inhibiting by blocking the action of AChase?