Cholinesterase

Definition

A family of enzymes (EC 3.1.1.7/8) that catalyze the hydrolysis of choline esters, principally terminating synaptic transmission by breaking down the neurotransmitter acetylcholine into choline and acetate. In arthropods, cholinesterases are concentrated in the central nervous system and neuromuscular junctions, where they regulate excitatory signaling. In entomological toxicology, this enzyme is the primary molecular target of organophosphate and carbamate insecticides, which inhibit its activity and cause uncontrolled neural firing, paralysis, and death in insects.

Etymology

From choline (the quaternary ammonium alcohol component of acetylcholine) + esterase (enzyme hydrolyzing ester bonds)

Example

In honey bees (Apis mellifera), acetylcholinesterase inhibition by neonicotinoid exposure—though neonicotinoids primarily target nicotinic receptors—can synergize with organophosphate cholinesterase inhibitors like chlorpyrifos, increasing colony mortality risk through sublethal neurotoxic effects on foraging behavior and navigation.

Synonyms

• choline esterase
• acylcholine acylhydrolase

Related Terms

• Acetylcholine
• Synapse
• Neurotransmitter
• Organophosphate
• carbamate
• insecticide resistance
• Mode of action
• neurotoxicology

Usage Notes

Distinguish between acetylcholinesterase (AChE, specific for acetylcholine, EC 3.1.1.7) and butyrylcholinesterase (pseudocholinesterase, broader substrate specificity, EC 3.1.1.8); in insects, AChE is the toxicologically relevant form. In resistance monitoring, modified AChE with reduced inhibitor binding is a documented resistance mechanism in mosquitoes (e.g., Culex pipiens) and agricultural pests. Cholinesterase activity assays are standard in biomonitoring for pesticide exposure in beneficial insects and in environmental toxicology.