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Molecular Forms of Acetylcholinesterase from Human Caudate Nucleus: Comparison of Salt‐Soluble and Detergent‐Soluble Tetrameric Enzyme Species
Author(s) -
Gennari K.,
Brodbeck U.
Publication year - 1985
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1985.tb12871.x
Subject(s) - chemistry , acetylcholinesterase , ionic strength , enzyme , biochemistry , molecular mass , dimer , sodium dodecyl sulfate , caudate nucleus , polyacrylamide gel electrophoresis , protein subunit , gel electrophoresis , chromatography , differential centrifugation , micelle , biology , aqueous solution , organic chemistry , gene , endocrinology
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 inter‐subunit disulfide bridges.