Relation between low erythrocyte acetylcholinesterase activity and membrane lipids in paroxysmal nocturnal...

Acetylcholinesterase of intact erythrocytes, their ghost and salt soluble extracts obtained from patients with paroxysmal nocturnal haemoglobinuria (PNH) does not differ from normal with respect to Km values for acetylthiocholine, and Ki values for phenyltrimethylammonium iodide. However, the enzyme from PNH sources has lower V max values than normal, has different thermal stability from normal, has less distinctive transition temperature in the Arrhenius plots, and is less subject to inhibition by stearic acid. These results and that from comparison of activation of deoxycholate-extracted enzyme by lipids from normal erythrocytes suggest that the low acetylcholinesterase activity in PNH erythrocytes is due, at least in part, to alteration in the lipid environment of the enzyme.