title: Effect of fructose 1-phosphate on the activation of liver glycogen synthase.
abstract: The activation (dephosphorylation) of glycogen synthase and the inactivation (dephosphorylation) of phosphorylase in rat liver extracts on the administration of fructose were examined. The lag in the conversion of synthase b into a was cancelled, owing to the accumulation of fructose 1-phosphate. A decrease in the rate of dephosphorylation of phosphorylase a was also observed. The latency re-appeared in gel-filtered liver extracts. Similar latency was demonstrated in extracts from glucagon-treated rats. Addition of fructose 1-phosphate to the extract was able to abolish the latency, and the activation of glycogen synthase and the inactivation of phosphorylase occurred simultaneously. Fructose 1-phosphate increased the activity of glycogen synthase b measured in the presence of 0.2-0.4 mM-glucose 6-phosphate. According to kinetic investigations, fructose 1-phosphate increased the affinity of synthase b for its substrate, UDP-glucose. The accumulation of fructose 1-phosphate resulted in glycogen synthesis in the liver by inducing the enzymic activity of glycogen synthase b in the presence of glucose 6-phosphate in vivo and by promoting the activation of glycogen synthase.
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D004789:Enzyme Activation / Q000187:drug effects; D005636:Fructosephosphates / Q000494:pharmacology*; D005934:Glucagon / Q000494:pharmacology; D006006:Glycogen Synthase / Q000378:metabolism*; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D006005:Phosphorylases / Q000037:antagonists & inhibitors; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D005636:Fructosephosphates; D007527:Isoenzymes; C032284:fructose-1-phosphate; D005934:Glucagon; D006005:Phosphorylases; D006006:Glycogen Synthase