Abstract
More than 80% of the acetylcholinesterase present in porcine erythrocyte membrane could be released from it by repeated washing with hypotonic buffer, as was true in the case of bovine erythrocyte. Density-gradient centrifugation revealed that the released enzyme particles of either species of mammals have a similar density of about 1.07 which is significantly lower than that of the original stroma. It has phospholipid and cholesterol contents higher than those of the stroma. Introduction of dinitrophenyl residue to the outer surface of the erythrocyte membrane caused about 60% inhibition of the acetylcholinesterase activity in all of human, bovine and porcine erythrocytes. Penicillin bound to the erythrocyte membrane exerted almost complete inhibition of the enzyme activity in all cases. These results suggest that acetylcholinesterase of similar nature is present in a form of lipoprotein on the outer surface of the erythrocyte membrane, with a density lower than that of the main part of the membrane.
