title: Molecular forms of acetylcholinesterase from human caudate nucleus: comparison of salt-soluble and detergent-soluble tetrameric enzyme species.
abstract: Extraction of human caudate nucleus under high-ionic-strength conditions solubilized 20-30% of total acetylcholinesterase (AChE) activity. Density gradient centrifugation revealed monomeric (5.0 S) and tetrameric (11.0 S) enzyme species. The purified, tetrameric salt-soluble (SS) AChE sedimented at 10.6 S and did not bind detergents. It showed an immunochemical reaction of identity with the detergent-soluble (DS) AChE species from human caudate nucleus and human erythrocytes, but did not cross-react with antibodies raised against human serum cholinesterase. The remaining activity was solubilized under low-ionic-strength conditions in the presence of 1.0% Triton X-100. The purified tetrameric, DS-AChE sedimented at 10.0 S as detergent-protein mixed micelle and on extensive removal of the detergent this enzyme formed defined aggregates by self-micellarization. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions revealed that the salt-soluble and detergent-soluble tetrameric enzyme species both contained a heavy and a light dimer; under reducing conditions mainly one band corresponding to the light subunit was seen. Molecular weights of 300,000 dalton and 280,000 dalton were calculated for SS-AChE and DS-AChE, respectively. Limited digestion of DS-AChE with proteinase K led to isolation of an enzyme that no longer bound detergents and lacked the intersubunit disulfide bridges.
mesh_terms: D000110:Acetylcholinesterase / Q000032:analysis* / Q000276:immunology; D002421:Caudate Nucleus / Q000201:enzymology*; D003429:Cross Reactions; D003902:Detergents; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007122:Immunoelectrophoresis; D046911:Macromolecular Substances; D008970:Molecular Weight; D009994:Osmolar Concentration; D012995:Solubility
chemical_list: D003902:Detergents; D046911:Macromolecular Substances; D000110:Acetylcholinesterase