cholinesterase

n.
An enzyme found primarily at nerve endings that catalyzes the hydrolysis of acetylcholine into acetic acid and choline.

[CHOLIN(E) + ESTERASE.]

(kō′lines′tərās)
n

An esterase that hydrolyzes acetylcholine. It is an enzyme that is widely distributed throughout the muscles, glands, and nerves of the body and that converts acetylcholine into choline and acetic acid.

An enzyme that splits acetylcholine into acetic acid and choline. Called also acetylcholinesterase.
This enzyme is present throughout the body, but is particularly important at the neuromuscular junction, where the nerve fibers terminate. Acetylcholine is released when a nerve impulse reaches a neuromuscular junction. It diffuses across the synaptic cleft and binds to cholinergic receptors on the muscle fibers, causing them to contract. Cholinesterase splits acetylcholine into its components, thus stopping stimulation of the muscle fibers. The end products of the metabolism of acetylcholine are taken up by nerve fibers and resynthesized into acetylcholine.

• c. inhibitor — the drugs neostigmine, physostigmine and pyridostigmine inhibit cholinesterase. These drugs are used to treat myasthenia gravis, a disease in which the cholinergic receptors are attacked by autoantibodies. The drugs extend the effect of acetylcholine on the muscle fiber.
• c. reactivator — choline-reactivating oximes are effective antidotes in organophosphorus insecticide poisoning, a state of acetylcholine excess because of cholinesterase inhibition. 2-PAM (2-pyridine aldoxime methchloride) is the most popular oxime for this purpose.

IN BRIEF: n. - An enzyme that is found especially in blood plasma

Tutor's tip: This word was used in the 2006 Scripps National Spelling Bee finals.