Terminates signal transduction at the neuromuscular junction by rapid hydrolysis of the acetylcholine released into the synaptic cleft. May be involved in cell-cell interactions. acetylcholine + H2O = acetate + choline + H(+) Inhibited by substrate concentrations above 0.5 mM. Isoform H form is a homodimer; the asymmetric form is a disulfide-bonded oligomer composed of a collagenic subunit (Q) and a variable number of T catalytic subunits. Attached to the membrane through disulfide linkage with the collagenic subunit, itself bound to the membrane. Additional isoforms seem to exist. Found in the synapses and to a lower extent in extrajunctional areas of muscle and nerve, and on erythrocyte membranes. An interchain disulfide bond is present in what becomes position 593 of the T isoform. GPI-anchored form. Belongs to the type-B carboxylesterase/lipase family.