Acetylcholinesterase

Acetylcholinesterase (acetylcholine hydrolase, E.C. 3.1.1.7) (AChE) is a widely distributed enzyme (Nachmansohn, 1959; Koelle, 1963) present, in particular, in excitable membranes of nerve and muscle, but also at other sites, such as the erythrocyte membrane (Mendel et al., 1943) and cobra venom (Zeller, 1948). The function of AChE in the postsynaptic membrane of cholinergic synapses is believed to be termination of synaptic transmission by the hydrolysis of acetylcholine (ACh), but its role in, for example, extrajunctional membranes, presynaptic membranes, and erythrocyte membranes has not been established. The evidence that AChE is usually a membrane-bound enzyme is based on subcellular fractionation and on electron microscopy combined with histochemical studies (Whittaker et al., 1964; Karlin, 1965; Bloom and Barrnett, 1966; Rodriguez de Lores Arnaiz et al., 1967; Israël et al., 1970; Nachmansohn, 1970). However, the exact relationship of the enzyme to the membrane has not been clarified (Hall and Kelly, 1971; Cohen et al., 1972).