Influence of the naturally occurring polyamines spermine, spermidine and putrescine on the kinetic properties of acetylcholinesterase. Comparative studies with the acetylcholinesterases from the central nervous system of Manduca sexta and of the synaptic plasma membrane of rat brain

1. Polyamines regulate the activity of the acetylcholinesterase from the central nervous system of the tobacco hornworm Manduca and from the synaptic plasma membrane of rat brain. 2. The acetylcholinesterase from Manduca is more sensitive to polyamines than the acetylcholinesterase from rat brain. 3. Polyamines enhance the affinity of both acetylcholinesterases for the substrate. 4. Both acetylcholinesterases show negative cooperativity, but in presence of physiological concentrations of polyamines the negative cooperativity is eliminated. 5. The effect of polyamines on acetylcholinesterase is not due to changes in the fluidity of the membrane.