What does cholinesterase mean?
Cholinesterase is any of a class of enzymes that breaks down choline esters, most importantly acetylcholine, the neurotransmitter that carries signals across the gaps between nerve cells and between nerves and muscles. By rapidly destroying acetylcholine after each signal, cholinesterase allows neurons to reset and fire again cleanly; without it, nerve impulses would fire uncontrollably. Biochemists distinguish two main forms: acetylcholinesterase, located at synaptic junctions, and butyrylcholinesterase, circulating in blood plasma. The enzyme has enormous practical significance: many insecticides and chemical weapons known as organophosphates act by inhibiting cholinesterase, while certain drugs for Alzheimer's disease and myasthenia gravis work by gently slowing it to boost remaining acetylcholine levels. Measuring blood cholinesterase activity is also a standard test for pesticide exposure. The word derives from 'choline', the compound whose esters the enzyme cleaves, combined with '-ase', the standard suffix for enzymes.
nounAn enzyme in the body that breaks down acetylcholine and other choline esters, thereby terminating nerve signal transmission at synapses.
- Any enzyme that hydrolyses choline esters, especially acetylcholine, terminating neurotransmission at cholinergic synapses.
"Organophosphate pesticides work by inhibiting cholinesterase, causing acetylcholine to accumulate at nerve junctions."
"Blood tests revealed sharply depressed cholinesterase levels, confirming exposure to an organophosphate insecticide."
"Donepezil, a cholinesterase inhibitor, modestly improves cognitive symptoms in some patients with Alzheimer's disease."
The plural appears mainly in scientific writing when distinguishing the two principal types, acetylcholinesterase and butyrylcholinesterase, or comparing enzymes across species.
"Vertebrates possess two main cholinesterases, each encoded by a different gene."
Nerve gas, pesticide poisonings, and Alzheimer's drugs all converge on one tiny enzyme: block cholinesterase and your muscles stop listening to your brain.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cholinesterase
Cholinesterase was named by combining three elements: 'choline', the nitrogen-containing compound whose esters the enzyme hydrolyses, 'ester', reflecting its substrate chemistry, and '-ase', the suffix coined around the end of the nineteenth century for enzymes (from Greek 'diastasis', separation). The root 'chol-' ultimately comes from the ancient Greek 'kholē', meaning bile, the same root that gives us 'cholesterol', 'cholera', and other biochemical terms. The name arose in early twentieth-century physiological research into how nerve impulses are chemically transmitted and switched off.
How cholinesterase is actually used
A technical term used almost exclusively in biochemistry, pharmacology, toxicology, and clinical medicine. In practice it refers to either of two distinct enzymes: acetylcholinesterase (also called 'true' cholinesterase), found at nerve synapses and red blood cells, and butyrylcholinesterase ('pseudo'cholinesterase), found mainly in blood plasma and the liver. Writers usually specify which type they mean when precision matters.
Easily confused with cholinesterase
Choline is a nutrient and chemical precursor of acetylcholine itself, whereas cholinesterase is the enzyme that degrades acetylcholine.
Cholesterol is a lipid found in cell membranes and blood, while cholinesterase is an enzyme involved in nerve signalling; the two share only a Greek root relating to bile.