Lipid-protein interactions in human erythrocyte-membrane acetylcholinesterase. Modulation of enzyme activity by lipids.
Purified human erythrocyte membrane acetylcholinesterase was incorporated into vesicles of various lipid compositions. The activities of the free and the lipid-associated enzyme were assayed at temperatures between 4 degrees C and 40 degrees C and the results were visualized as plots of log v versus 1/T (Arrhenius plots). For the purified, detergent-depleted enzyme a linear relation was obtained. If Triton X-100 was added to the assay medium a curved plot resulted. For acetylcholinesterase incorporated into dimyristoylphosphatidylcholine vesicles a clear break in the plot was observed at the phase transition temperature of the lipid. With lipids not experiencing a phase transition within the temperature range investigated, again a linear relation was obtained. These results show that the activity of human erythrocyte membrane acetylcholinesterase is strongly modulated by its hydrophobic environment.
D000110:Acetylcholinesterase / Q000097:blood*; D002784:Cholesterol / Q000494:pharmacology; D002800:Cholinesterase Inhibitors; D004134:Dimyristoylphosphatidylcholine; D004910:Erythrocyte Membrane / Q000201:enzymology*; D004912:Erythrocytes / Q000201:enzymology*; D005614:Freeze Fracturing; D006801:Humans; D008081:Liposomes; D008854:Microscopy, Electron; D017830:Octoxynol; D010713:Phosphatidylcholines / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000494:pharmacology; D012969:Sodium Fluoride / Q000494:pharmacology; D013816:Thermodynamics
D002800:Cholinesterase Inhibitors; D008081:Liposomes; D010713:Phosphatidylcholines; D011092:Polyethylene Glycols; D012969:Sodium Fluoride; D017830:Octoxynol; D002784:Cholesterol; D000110:Acetylcholinesterase; D004134:Dimyristoylphosphatidylcholine