Acetylcholinesterase hydrolyzes the neurotransmitter| acetylcholine at neuromuscular junctions and brain cholinergic synapses| and thus terminates signal transmission. It is also found on the red blood cell membranes| where it constitutes the Yt blood group antigen. Acetylcholinesterase exists in multiple molecular forms which possess similar catalytic properties| but differ in their oligomeric assembly and mode of cell attachment to the cell surface. It is encoded by the single ACHE gene| and the structural diversity in the gene products arises from alternative mRNA splicing| and post-translational associations of catalytic and structural subunits. The major form of acetylcholinesterase found in brain| muscle and other tissues is the hydrophilic species| which forms disulfide-linked oligomers with collagenous| or lipid-containing structural subunits. The other| alternatively