The allosteric transitions from membrane-bound enzymes: Behavior of erythrocyte acetylcholinesterase from fat-deficient rats

Abstract

The allosteric behavior of acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) from red cell ghosts of rats fed fat-sufficient and fat-deficient diets was investigated. Allosteric type kinetics with n = −1.6 have been obtained for the inhibition by F- in rats fed a fat-sufficient diet. In animals fed a fat -sufficient diet the values on n changed form −1.6 to −1.0. When these animals were then fed rats fed a fat-sufficient diet the values of n shifted from −1.0 to −1.6. This in vivo reversion was obtained after 8 days of refeeding. Two types of changes in the values of n were obtained in vitro in fat-deficient rats: (1) from −1.0 to −1.6 by solubilization of the membrane-bound enzyme with Triton X-100, (2) from −1.6 to −1.0 by resconstitution of the membrane-like structure from the soluble enzymatic preparation. The possibility that the structure of the membrane could be responsible for the changes in the phenomenon of phenotypic allosteric desensitization in the membrane-bound enzymes is discussed