[Membrane-associated acetylcholinesterase in the sarcotubular system of skeletal muscles]

Isolated membranes of the sarcotubular system of the skeletal muscle of the rabbit exhibit acetylcholinesterase activity. The activity of the enzyme depends on the intactness of the vesicles, it increases with time and after the action of detergents, suggesting that the enzyme may be bound to the membranes in a latent occluded form. The optimal conditions of the hydrolytic reaction were determined to be at the protein concentration of 35-40 micrograms/ml. The most suitable pH for acetylcholinesterase activity was found to be in the mildly alkaline region of pH = 8.0. The dependence of the activity of the enzyme on the concentration of the substrate displayed a hyperbolic course, the reciprocal dependence according to Lineweaver and Burk yielded the values KM = 0.69 mmol.l-1 and Vmax = 1.99 mumol/mg/h. The observed properties of acetylcholinesterase from the sarcotubular system show that the enzyme is associated with these membranes and after the action of detergents it has a well measurable activity.