Effect of sevin on kinetic parameters of camel retina acetylcholinesterase

The present investigation addresses the effect of sevin (insecticide) on kinetic parameters of camel retina membrane-bound acetylcholinesterase (AChE, EC 3.1.1.7). The Michaelis-Menten constant (Ks) for the hydrolysis of acetylthiocholine iodide (ASCh) by AChE was 0.072 mM in the control system, a value decreased by 38-55% in the sevin treated systems. The Vmax was 0.967 mumole/min/mg protein for the control system while it was decreased by 50-84% in the sevin treated systems. The Lineweaver-Burk plot, Dixon plot, and their secondary replots indicated that the nature of the inhibition was of the linear mixed type, i.e. uncompetitive and noncompetitive. The values of Ki(slope) and KI(intercept) were estimated as 6.194 and 2.811 microM, respectively. The turnover number (Kcat) and specificity constant (Ksp) were 74.65 min-1 and 10.37 x 10(5) (M.min)-1 in the control system respectively, while the values for both parameters were significantly decreased in the sevin treated systems.