The catalytic activity of membrane-bound acetylcholinesterase
in electric organ tissue was shown to be governed by diffusion-
controlled substrate and hydrogen ion gradients, generated by
acetylcholinesterase-catalysed hydrolysis leading to a lower substrate
concentration and pH in the vicinity of the particulate
enzyme.
Various solubilization procedures, including extraction with
salts and detergents, chemical modification proteolysis showed that
interaction of most of the acetylcholinesterase with the excitable
membrane is primarily electrostatic, but that part of the enzyme
seems to be more intimately associated with the membrane.
\u27Native\u27 acetylcholinesterase, as isolated from fresh electric
organ tissue, is a complex molecular structure in which a multisubunit
head is connected to an elongated tail. Proteolytic digestion
or autolysis leads to detachment of the tail and conversion of
acetylcholinesterase to a globular tetramer containing four similar
subunits in which each pair is connected by disulfide bonds. Further
digestion leads to cleavage of the individual polypeptide chains of
the subunits which are not, however, released unless the enzyme
is denatured. The possible modes of attachment of the \u27native\u27
acetylcholinesterase molecule to the excitable membrane are
discussed
