Cholinesterase

acetylcholinesterase (Yt blood group)
Diagram of Pacific electric ray acetylcholinesterase. From PDB: 1EA5​.
Identifiers
Symbol	ACHE
Alt. symbols	YT
Entrez	43
HUGO	108
OMIM	100740
RefSeq	NM_015831
UniProt	P22303
Other data
EC number	3.1.1.7
Locus	Chr. 7 q22

butyrylcholinesterase
Cartoon diagram of human butyrylcholinesterase. From PDB: 1P0I​.
Identifiers
Symbol	BCHE
Alt. symbols	CHE1, CHE2, E1
Entrez	590
HUGO	983
OMIM	177400
RefSeq	NM_000055
UniProt	P06276
Other data
EC number	3.1.1.8
Locus	Chr. 3 q26.1-26.2

In biochemistry, a cholinesterase or choline esterase is an esterase that lyses choline-based esters, several of which serve as neurotransmitters. Thus, it is either of two enzymes that catalyze the hydrolysis of these cholinergic neurotransmitters, such as breaking acetylcholine into choline and acetic acid. These reactions are necessary to allow a cholinergic neuron to return to its resting state after activation. For example, in muscle contraction, acetylcholine at a neuromuscular junction triggers a contraction; but for the muscle to relax afterward, rather than remaining locked in a tense state, the acetylcholine must be broken down by a choline esterase. The main type for that purpose is acetylcholinesterase (also called choline esterase I or erythrocyte cholinesterase); it is found mainly in chemical synapses and red blood cell membranes. The other type is butyrylcholinesterase (also called choline esterase II or plasma cholinesterase); it is found mainly in the blood plasma.

The two types of cholinesterase are acetylcholinesterase (ACHE) and butyrylcholinesterase (BCHE). The difference between the two types has to do with their respective preferences for substrates: the former hydrolyses acetylcholine more quickly; the latter hydrolyses butyrylcholine more quickly.