Abdulaziz A. Al-Jafari, Fareeda Al-Khwyter, Mohammad A. Kamal and Abdullah S. Alhomida
Department of Biochemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
Abstract: This work addresses the kinetic analysis of the interaction of methotrexate (MTX) with camel retina acetylcholinesterase (AChE, EC 3.1.1.7). It was found that the MTX effect was reversible in nature. The IC50 was determined, by two methods, to be 1.362 mM. The Michaelis-Menten constant (Ks) for the hydrolysis of acetylthiocholine iodide (ASCh) by AChE was 0.123 mM in the control system, and the MTX-treated systems showed a 10 - 35% decrease in this value. The Vmax was 0.789 micromol/min/mg protein for the control system, while it was decreased by 23 - 76% in the MTX-treated systems. The Lineweaver- Burk plot, Dixon plot and their secondary replots indicated that the inhibition was a linear mixed type; i.e., uncompetitive and noncompetitive. The values of Ki and KI were estimated as 0.782 and 0.404 mM, respectively. The use of camel retina as a model for the study of human retina may open new avenues for studying various aspects of AChE.
Keywords:
Acetylcholinesterase, Kinetics, Inhibition, Methotrexate, Retina