Optimization and kinetic studies of human erythrocyte membrane-bound acetylcholinesterase.

The human erythrocyte membrane-bound acetylcholinesterase was characterized with respect to optimal assay conditions for its kinetic properties. It was found that 40.0 micrograms protein and 5.0 min incubation time were the suitable concentration of AChE protein and reaction time for the linearity of AChE activity at 25 degrees C. The Vmax for the AChE was 35% higher in the presence of 25 mM sodium phosphate buffer than 25 mM Tris-HCl buffer. The AChE activity was assayed at various strengths of sodium phosphate buffer (0.0125-0.20 M), and the optimum strength was found to be 0.05 M. The optimum substrate (ASCh) concentration was found to be 5.0 mM whereas at higher substrate concentrations, the AChE activity declined. The ASCh concentration ranges for different orders of the reactions were determined and kinetic parameters (Km, Vmax, Kcat and Ksp) were established at each order of the reaction.