In contrast to most other small-molecule neurotransmitters, the postsynaptic action of ACh at many cholinergic synapses (the neuromuscular junction in particular) are not terminated by reuptake but by a powerful hydrolytic enzyme, acetylcholinesterase (AChE). This enzyme is concentrated in the synaptic cleft, ensuring a rapid decrease in ACh concentration after its release from the presynaptic terminal. AChE has a very high catalytic activity (about 5000 molecules of ACh per AChE molecule per second) and hydrolyzes ACh into acetate and choline. As already mentioned, cholinergic nerve terminals typically contain a high-affinity, Na+-choline transporter that takes up the choline produced by ACh hydrolysis.