Isolation and characterization of liver glycogen synthase from diabetic rats

Abstract

Glycogen synthase was isolated from the livers of alloxan diabetic rats by the addition of a high-molecular-weight, polydisperse glycogen, described previously ( D. M. Haverstick and A. H. Gold, 1981, Anal. Biochem. III, 137–145 ), to supernatant extracts of centrifuged liver homogenates. Further purification was achieved by high-speed centrifugation and ion-exchange chromatography. Comparative polyacrylamide gel electrophoresis show that synthase isolated from normal and diabetic rats have the same subunit molecular weight. Enzymes from both sources react with antisynthase antibody in the same manner. Both enzymes have essentially the same affinity toward substrate, UDP-Glc, and activator, Glc-6-P, and both enzymes are capable of undergoing b into a transformation in vitro with exogenous, partly purified synthase phosphatase. These results suggest that diabetes does not result in the in vivo appearance of an “abnormal” type of glycogen synthase which is not capable of interacting with the synthase b to a conversion system.