Abstract
Kinetic parameters for the effect of cyclophosphamide (CP) on the camel retina acetylcholinesterase (AChE) activity were investigated for the first time in the present study. It was found that 18 μg of retina protein and an incubation time of 4.0 min were suitable conditions for linear of AChE activity. The CP effect was independent of time of incubation with AChE before the addition of substrate, which shows its reversible action. Moreover, dilution data prove that CP is a reversible inhibitor of camel retina AChE. Cyclophosphamide (0.2–2.4 mM) inhibited activity of camel retina in a concentration-dependent fashion, the IC
50, being about 1.17 mM. The Michaelis constant (
K
m) for the hydrolysis of acetylthiocholine iodide was found to be 0.106 mM and the
V
max was 0.765 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 pure noncompetitive type. The value of
K
i was estimated as 0.763 μM by the primary Dixon and secondary replots of the Lineweaver-Burk plot.