Butyrylcholinesterase: Substrates

Butyrylcholinesterase (pseudocholinesterase) is a serine hydrolase synthesized in the liver and present in the plasma. It is structurally and functionally related to acetylcholinestrase, an enzyme that is that catalyzes the hydrolysis of acetylcholine. Butyrylcholinesterase catalyzes the hydrolysis of esters of choline, including acetylcholine, butyrylcholine, and succinylcholine, as well as the hydrolysis of esters such as cocaine, acetylsalicylic acid and heroin.

Succinylcholine is hydrolyzed to succinylmonocholine and choline. When succinylcholine is injected intravenously, about 90% of its dose is hydrolyzed by BChE within 1 min and only 10% reaches the neuromuscular junction. Because little or no butyrylcholinesterase is present at the neuromuscular junction, the neuromuscular blockade of succinylcholine is terminated by its diffusion away from the neuromuscular junction into the circulation. The effect of butyrylcholinesterase on onset and duration of action of succinylcholine is therefore exerted by the rate of hydrolysis of succinylcholine before it reaches, and after it leaves the NMJ.

Mivacurium, an benzylisoquinolinium neuromuscular blocker is also metabolized by butyrylcholinesterase to a monoester and a dicarboxylic acid at 70% to 88% the rate at which succinylcholine is.

Both usual and atypical butyrylcholinesterase can hydrolyze aspirin with the same kinetic manner. Butyrylcholinesterase is also important in scavenging naturally occurring (physostigmine) and synthetic (organophosphate) anticholinesterases.