Abstract
For the first time, kinetic parameters of the effect of tacrine, an anti-cholinesterase inhibitor of therapeutic potential in Alzheimer’s disease has been studied on human retinal acetyl-cholinesterase (AChE). Tacrine inhibited the AChE activity in a concentration dependent manner, the IC
50 being about 45 nM. The Michaelis–Menten constant (
K
m) for the hydrolysis of acetylthiocholine iodide was found to be 0.120 mM and this value was increased by 4–52.8% in the presence of tacrine.
V
max was observed to be 2.23 μmol/h per mg protein for the control system, while it was decreased by 14.73–56.25% in the tacrine treated systems. Dixon as well as Lineweaver–Burk plots and their secondary replots indicated that the nature of the inhibition was of the mixed type, i.e. a combination of competitive and noncompetitive inhibition. The values of
K
i and
K
I were estimated to be as 37.76 and 64.36 nM, respectively.