Butyrylcholinesterase (BChE) is an enzyme widely distributed throughout the body in humans, but particularly prevalent in serum, where it occurs as a tetramer of catalytic subunits. It is distinguished from the homologous enzyme, acetylcholinesterase, by its ability to hydrolyze the non-natural substrate butyrylcholine as well as the neurotransmitter, acetylcholine. Its biological role remains obscure, but mutations in the human BCHE gene result in prolonged post-surgical apnea due to the inability of the mutant BChEs to hydrolyse the local anaesthetic, succinylcholine. BChE finds medical use as a bioscavenger for overcoming organophosphate (OP) nerve agent and insecticide intoxication by interacting rapidly with the toxic agents. Crystal structures of both the native enzyme and of its conjugates with nerve agents are available. The image at the right correspond to one representative BChE, i.e. the crystal structure of recombinant full length human butyrylcholinesterase (2pm8).
