Relation between Low Erythrocyte Acetylcholinesterase Activity and Membrane Lipids in Paroxysmal Noctural Haemoglobinuria*

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Abstract
Acetylcholinesterase of intact erythrocytes, their ghosts and salt soluble extracts obtained from patients with paroxysmal nocturnal hemoglobinuria (PNH) did not differ from normal with respect to Km values for acetylthiocholine, and Ki values for phenyltrimethylammonium iodide. The enzyme from PNH sources had lower Vmax values than normal, had different thermal stability from normal, had less distinctive transition temperature in the Arrhenius plots and was less subject to inhibition by stearic acid. These results and that from comparison of activation of deoxycholate-extracted enzyme by lipids from normal erythrocytes suggested that the low acetylcholinesterase activity in PNH erythrocytes was due, at least in part, to alteration in the lipid environment of the enzyme.