Malathion-induced inhibition of human plasma cholinesterase studied by the fluorescence spectroscopy method
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The in vitro effect of technical grade malathion was assessed via the kinetic parameters of human plasma butyrylcholinesterase (BChE) using N-methylindoxyl acetate as a substrate for BChE. An inhibitor kinetics study demonstrated the existence of a biphasic inhibition curve, indicating high-and low-affinity binding sites of malathion. The IC (50) values as calculated from the experimental inhibition curves were 1.33 x 10(-9) and 1.48 x 10(-5) M for the high-and low-affinity binding sites, respectively; Hills analysis gave 1.29 x 10(-9) and 1.38 x 10(-6) M. The Cornish-Bowden plots and their secondary plots indicated that the nature of inhibition was of mixed type with the predominant competitive character of both affinity binding sites.