Acetylcholinesterase (AChE or acetylhydrolase) is a hydrolase that hydrolyzes the neurotransmitter acetylcholine. AChE is found at mainly neuromuscular junctions and cholinergic brain synapses, where its activity serves to terminate synaptic transmission. It belongs tocarboxylesterase family of enzymes. It is the primary target of inhibition by organophosphorus compounds such as nerve agents and pesticides. AChE has a very high catalytic activity - each molecule of AChE degrades about 25000 molecules ofacetylcholine (ACh) per second, approaching the limit allowed by diffusion of the substrate. ACh is released from the nerve into the synaptic cleft and binds to ACh receptors on the post-synaptic membrane, relaying the signal from the nerve. AChE, also located on the post-synaptic membrane, terminates the signal transmission by hydrolyzing ACh. The liberated choline is taken up again by the pre-synaptic nerve and ACh is synthetized by combining with acetyl-CoA through the action of choline acetyltransferase.
(-)-Huperzine A (Huperzine A) 是从中国梅花苔中分离得到的生物碱，具有神经保护活性。(-)-Huperzine A 是一种高效、高特异性、可逆的，具有血脑屏障渗透性的乙酰胆碱酯酶 (AChE) 抑制剂， 其 IC50 值为 82 nM。 (-)-Huperzine A 也是 N-甲基-D-天冬氨酸 (NMDA) 受体的非竞争性拮抗剂。(-)-Huperzine A 被开发用于神经退行性疾病的研究，包括阿尔茨海默病。
