In biochemistry, cholinesterase is an enzyme that catalyzes the hydrolysis of the neurotransmitter acetylcholine into choline and acetic acid, a reaction necessary to allow a cholinergic neuron to return to its resting state after activation.
The difference between the two types of cholinesterase has to do with their respective preferences for substrates: the former hydrolyses acetylcholine more quickly; the latter hydrolyses butyrylcholine more quickly.
Clinically-useful quantities of butyrylcholinesterase were synthesized in 2007 by PharmAthene, through the use of genetically-modified goats.
Elevation of plasma pseudocholinesterase was observed in 90.5% cases of acute myocardial infarction.
The presence of acetylcholinesterase in the amniotic fluid may be tested in early pregnancy. A sample of amniotic fluid is removed by amniocentesis, and presence of AChE can confirm several common types of birth defect, including abdominal wall defects and neural tube defects.
Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen. The entry on Lawesson's reagent has some details on one sub-class of the phosphorus-based compounds.
Outside of biochemical warfare, anticholinesterases are also used in anesthesia or in the treatment of myasthenia gravis, glaucoma, and Alzheimer's disease. Also, such compounds are used for killing insects in a range of products including sheep dip, organophosphate pesticides, and carbamate pesticides. In addition to acute poisoning as described above, a semi-acute poisoning characterized by strong mental disturbances can occur. Also, prolonged exposure can cause birth defects.