A New Cholinesterase in Swine Serum

THERE are at present two groups of enzymes in mammals which hydrolyse acetylcholine: the first hydrolyses acetylcholine and acetyl-β-methylcholine and is found primarily in nervous tissue and red blood cells; the second group hydrolyses acetylcholine and benzoylcholine and is found in the serum and tissues of some animal species. Characteristic of this last group is the enzyme in human serum. In addition, there is one other related enzyme or group of enzymes which hydrolyses benzoylcholine but not acetylcholine. This was first noted and labelled benzoylcholinesterase by Sawyer 1 , and was reported by us as occurring in rabbit serum 2 .