THE ASSOCIATION OF ACETYLCHOLINESTERASE AND MEMBRANE IN SUBCELLULAR FRACTIONS OF THE ELECTRIC TISSUE OF ELECTROPHORUS

Abstract

Subcellular fractions of the electric tissue of the main organ of the eel Electrophorus electricus were prepared in sucrose media by differential centrifugation and differential discontinuous gradient centrifugation. The distributions of acetylchollnesterase, cytochrome oxldase, DNA, and protein were determined. The appearance of the fractions was determined by phase contrast microscopy and by electron microscopy. A fraction prepared by differential centrifugation at 30,000 g for 20 minutes in 0.89 [image] sucrose contained 63% of the total acetylcholinesterase activity at 4 times the specific activity of that of the tissue homogenate. A subtraction prepared by centrifugation in a discontinuous density gradient showed a peak of total and relative specific acetylcholinesterase activity of 35% and 1.9, respectively. The average over-all purification was 7 times. The acetylcholinesterase peak was below the cytochrome oxidase peak and above the DNA peak in the density gradient. The presence of acetylcholinesterase in the fractions was correlated with the presence of large fragments of the cell membrane; however, the presence of other tissue components was noted. The acetylcholinesterase associated with membrane was found to be activated by incubation with sodium deoxycholate. The possible use of the peak fraction containing membranes rich in acetylcholinesterase for the investigation of other components of the acetylcholine system and of other properties of the membrane is discussed.