Effect of Essential Fatty Acid Deficiency on the Arrhenius Plot of Acetylcholinesterase from Rat Erythrocytes

Abstract

Arrhenius plot of erythrocyte acetylcholinesterase was studied at different pH values in four groups of rats. Two groups were fed EFA-sufficient diets with lard or corn oil as the dietary fat. The other two groups were fed EFA-deficient diets: a basic, fat-free diet, and the same supplemented with hydrogenated beef fat. The Arrhenius plot of membrane-bound acetylcholinesterase from EFA-sufficient animals was found to have a breakpoint about 20° at pH 8.0, with lower activation energy at higher temperatures. The enzyme from EFA-deficient animals exhibited a breakpoint about 28°, the activation energies being lower than that of the enzyme from EFA-sufficient animals above and below this point. Solubilization of the membrane with Triton X-100 led to a shift in the breakpoint and to an increase in the activation energies in the enzyme from EFA-deficient animals. No changes were detected with preparations from EFA-sufficient animals after the treatment. After reconstitution of membrane-like material from the soluble EFA-deficient preparation, the distinctive enzymatic behavior was restored. The results indicate that the Arrhenius plot of the acetylcholinesterase is changed when the enzyme is bound to an EFA-deficient membrane.