Protein ligand interactions: alkylated pyridinium salts as inhibitors of acetylcholinesterase from Electrophorus electricus.

The interaction of alkyl-quaternary pyridinium hydrochloride salts on acetylcholinesterase (AChE, E.C. 3.1.1.7) has been investigated. Kinetic analysis has shown that they reflect a competitive inhibition with Ki values in the range 5-12 microM and 7-17 microM for ethyl- and methyl-substituted salts, respectively. Spectrophotometry was used to study the binding of the ligands with the enzyme and Scatchard analysis used to calculate the respective dissociation constants (Kd) and the number of binding sites. The substitution position of the alkyl group on the pyridine ring also influenced the binding capacity and the Ki values.