Cholinesterase is a family of enzymes that is involved in catalyzing the hydrolysis of the neurotransmitter acetylcholine (ACh) into choline and acetic acid. This terminates the action of acetylcholine, enabling cholinergic neurons to return to their proper resting state after activation, which facilitates proper muscle relaxation after contraction. This is the primary function of cholinesterase. 

Other functions of cholinesterase enzymes are to send signals through the nerves and help the nervous system to work correctly.