BCHE and Alzheimer disease: According to the cholinergic theory, cognitive impairment in AD is caused by the loss of acetylcholine-synthesizing cholinergic neurons and consequent drop in ACh levels.1 ACh is hydrolyzed toacetyl coenzyme A (acetyl CoA) and choline by two cholinesterases called acetylcholinesterase (AChE) and butyrylcholinesterase (BChE).