Acetylcholinesterase (AChE) is the primary cholinesterase in the body. It is an enzyme that catalyzes the breakdown of acetylcholine (a chemical released by nerves that activates muscle contractions) and of some other choline esters that function as neurotransmitters. Alzheimer's disease is a progressive neurodegenerative disorder which leads to irreversible loss of neurons that result in reduced level of acetylcholine neurotransmitter (ACh).

AChE is found in red cells and many types of conducting tissue: nerve and muscle, central and peripheral tissues, motor and sensory fibers, and cholinergic and noncholinergic fibers. The activity of AChE is higher in motor neurons than in sensory neurons.

Biological function

During neurotransmission, ACh is released from the presynaptic neuron 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 neuron and ACh is synthesized by combining with acetyl-CoA through the action of choline acetyltransferase.

A cholinomimetic drug disrupts this process by acting as a cholinergic neurotransmitter that is impervious to acetylcholinesterase's lysing action

Alzheimer's disease is a progressive neurodegenerative disorder associated with memory impairment and cognitive deficit. It is characterized by low levels of acetylcholine in the brain of Alzheimer's disease patients. According to the cholinergic hypothesis, the inhibition of acetylcholinesterase (AChE), an enzyme that catalyzes acetylcholine hydrolysis, increases the levels of acetylcholine in the brain, thus improving cholinergic functions in Alzheimer's disease patients. Furthermore, although the general consensus concludes that AChE inhibitors (AChEi) can alleviate Alzheimer's disease symptoms, they neither delay nor reverse the disease progress.

Memory loss and confusion are the main symptoms of the Alzheimer's disease. People having Alzheimer's disease may experience:

Cognitive: mental decline, difficulty thinking and understanding, confusion in the evening hours, delusion, disorientation, forgetfulness, making things up, mental confusion, difficulty concentrating, inability to create new memories, inability to do simple maths, or inability to recognise common things

Behavioural: aggression, agitation, difficulty with self care, irritability, meaningless repetition of own words, personality changes, lack of restraint, or wandering and getting lost

Mood: anger, apathy, general discontent, loneliness, or mood swings

Psychological: depression, hallucination, or paranoia

Whole body: loss of appetite or restlessness

Also common: behavioral symptoms, inability to combine muscle movements, or jumbled speech

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