[Inhibitory properties of cycloguanide phenylsulfone on acetylcholinesterase]

Mouse brain homogenates, mouse RBC, immobilized enzyme of pig brain, and human RBC were chosen as source of AChE, AChE activities were determined by colorimetric and gasometric methods. Cycloguanide phenylsulfone (CGP) exerted a moderate inhibitory effect on AChE. The pI50 (negative logarithm of molar concentration causing 50% inhibition of AChE) towards AChE in mouse RBC and brain were 5.75 and 5.50, respectively. The binding potency to AChE was very loose. The AChE inhibition was easily reversed by washing. It showed that CGP belonged to the contra-competitive AChE inhibitor.