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The molecular weight and subunit structure of acetylcholinesterase preparations from the electric organ of the electric EEL

1974; Elsevier BV; Volume: 59; Issue: 1 Linguagem: Inglês

10.1016/s0006-291x(74)80182-8

1090-2104

Yadin Dudai, Israel Silman,

Pesticide Exposure and Toxicity

Acetylcholinesterase (AChE) preparations obtained from electric organ tissue of Electrophorus electricus subsequent to tryptic digestion and/or autolysis had sedimentation coefficients of about 11 S and molecular weights of 320,000–350,000. These values did not significantly decrease upon prolonged autolysis. The major polypeptide in 11 S AChE had molecular weights of 82,000 ± 6,000 and 59,000 ± 4,000. The ratios of these two components was a function of the degree of autolysis of the tissue from which the enzyme was purified. In less autolysed tissue the principle component was the 82,000 one, while after prolonged autolysis the 59,000 component predominated. The appearance of the 59,000 component was accompanied by the appearance of polypeptides of ∼25,000. It is proposed that autolysis and/or proteolysis cleave the 82,000 polypeptide chain of native AChE into fragments of 59,000 and ∼25,000 which are retained in the quaternary structure of the enzyme unless it is denatured. Possible models for the quaternary structure and arrangement of disulfide bridges in 11 S AChE are discussed.