Butyrylcholinesterase

Butyrylcholinesterase (BChE), also known as pseudocholinesterase or serum cholinesterase, is an enzyme that plays a critical role in the process of cholinergic neurotransmission by hydrolyzing choline-based esters. Unlike its counterpart, acetylcholinesterase (AChE), which is found predominantly in nerve and muscle cells, BChE is found in the blood plasma and the liver. Its primary function is to break down choline esters such as butyrylcholine and acetylcholine, which is a neurotransmitter involved in various functions including muscle contraction and memory.

Function

BChE's main physiological role is to hydrolyze choline esters that are not suited for acetylcholinesterase. It serves as a biochemical scavenger by clearing various choline esters from the blood, thus preventing them from accumulating and exerting harmful effects. Additionally, BChE has a role in the metabolism of certain drugs, including muscle relaxants used in anesthesia, thereby influencing drug efficacy and safety.

Genetics

The gene encoding for butyrylcholinesterase is located on chromosome 3q26. BChE activity varies among individuals due to genetic polymorphisms. Some variants result in reduced enzyme activity, which can lead to prolonged effects of certain drugs metabolized by BChE, such as succinylcholine, a muscle relaxant used during surgery.

Clinical Significance

Alterations in BChE activity can be indicative of various medical conditions. Low levels of BChE may be observed in liver disease, malnutrition, and certain genetic disorders. Conversely, elevated BChE levels can be seen in obesity, diabetes, and in the acute phase response to inflammation or infection. Additionally, BChE inhibitors are being explored for their therapeutic potential in treating diseases characterized by cholinergic dysfunction, such as Alzheimer's disease.

Diagnostic Use

Measurement of BChE activity is used in the diagnosis and monitoring of certain medical conditions. For example, reduced BChE activity can confirm exposure to organophosphate pesticides, which are potent inhibitors of cholinesterases. Furthermore, genotyping for BChE variants can help predict individual responses to certain medications, aiding in personalized medicine.

See Also

• Acetylcholinesterase
• Cholinergic system
• Neurotransmitter
• Pharmacogenomics