Abstract
The effect of phenserine, a novel cholinesterase inhibitor, was assessed for the first time on kinetic parameters of human erythrocyte acetylcholinesterase (AChE). Phenserine (0.025-0.40 μM) inhibited the activity of human erythrocyte AChE in a concentration-dependent fashion, the IC50was 0.0453 μM. The Michaelis-Menten constant (Km) for the hydrolysis of acetylthiocholine iodide was found to be 0.124 mM and the Vmaxwas 0.980 μmol/min/mg protein. Dixon as well as Lineweaver-Burk plots and their secondary replots indicated that the nature of the inhibition was of the noncompetitive type. The value of Kiwas estimated as 0.048 μM by the primary and secondary replots of the Dixon as well as secondary replots of the Lineweaver-Burk plot. A novel relationship between Kiand substrate concentration was also identified which permits more precise prediction of the specific type of noncompetitive inhibition of various enzymes by a wide variety of drugs, chemicals and, in some circumstances, by their own substrates.