AbstractsBiology & Animal Science

Nuclear magnetic resonance has been used to study the association of atropine and eserine with acetylchol inesterase extracted from squid head ganglia and synaptosome membranes from rat brain cortex. Line width changes of the N-methyl and phenyl groups of atropine and the N-methyl and C-methyl groups of eserine resulting from association with the enzyme and the synaptosome membranes have been used to study the interactions. The results show that whereas eserine binds at the active site of the enzyme, atropine binds at a site distinct from the active center. Further proof that the binding sites of the two ligands are distinct from each other was obtained by showing that the antichol inesterase, tetraethyl pyrophosphate (TEPP) diminished the binding of eserine but not of atropine. The effect of pH, ionic strength and TEPP on the binding of synaptosome membranes was similar to the results obtained with soluble acetylchol inesterase. This indicates that both ligands bind to the synaptosome membrane bound acetylcholinesterase. The significance of the non-catalytic site on acetylchol inesterase in relation to the acetylcholine receptor is discussed.