There are two types of cholinesterases in humans, AChEand butyrylcholinesterase (BuChE). The cholinesterases differin their location in the body and their substrate specificity.AChE is associated with the outside surface of glialcells in the synapse and catalyzes the hydrolysis of ACh tocholine and acetic acid. Inhibition of AChE prolongs the durationof the neurotransmitter in the junction and producespharmacological effects similar to those observed whenACh is administered. These inhibitors are indirect-actingcholinergic agonists. AChE inhibitors have been used in thetreatment of myasthenia gravis, atony in the GI tract, andglaucoma. They have also been used as agricultural insecticidesand nerve gases. More recently, they have received attentionas symptomatic drug treatments in patients sufferingfrom Alzheimer disease.
BuChE (pseudocholinesterase) is located in humanplasma. Although its biological function is not clear, it hascatalytic properties similar to those of AChE. The substratespecificity is broader (Table 17.5), and it may hydrolyze dietaryesters and drug molecules in the blood.
