L'acétylcholinestérase des organes électriques de Poissons (torpille et gymnote); complexes membranaires

After extraction of the torpedo electric organ, three main molecular species, A, C, D, carrying the acetylcholinesterase activity have been found. This is observed in fresh‐frozen organ extracts, toluene‐autolysed organ extracts, or autolysis exsudate. A fourth species, B, appears during autolysis in the exsudate, or following treatment of the extracts by proteolytic enzymes, trypsin or α‐chymotrypsin. A series of agents such as pH, p ‐hydroxymercuribenzoate, or pharmacological drugs, have been tried in order to modify the distribution of activity among the different species; all have failed, demonstrating the stability of these species. The two species which migrate faster in a sucrose gradient, C and D, show the phenomenon of aggregation in low salt concentration (0.01 M), whereas and A and B, the slower species, do not. The buoyant density of the active species in our extract is the same as that of the purified enzyme; a high content of lipids seems therefore excluded. Species B in electric eel extracts (obtained after trypsic treatment) has been identified with the molecular form of the enzyme as recently purified and cristallized. This raises the question of the biological significance of this preparation, especially since one of the original species, A, has a smaller mass and is also converted into B during proteolysis.