Formation and breakdown of glycogen in the liver

Abstract

The breakdown of glycogen was studied in rabbit liver brei. The main pathway of glycogen breakdown in the liver is through phosphorylation with inorganic phosphate, the product being glueose-l-phosphate, which is then dephosphorylated to glucose. Only a small part (not more than 15%) of the glycogen breakdown in the liver is due to amylases. Reasons are given for the supposition that the above scheme represents the mechanism by which liver glycogen is converted to blood sugar in vivo. In presence of NaF, the dephosphorylation of glucose-l-phosphate is inhibited, and under these conditions, the glucose-1-phosphate formed by the phosphorylation of glycogen is all converted to hexose-6-phosphate. When glucose-1-phosphate is added to NaF-poisoned liver brei, part of it is converted to hexose-6-phosphate, and the rest to glycogen. Thus the reaction: glycogen + phosphate glucose-1-phosphate is shown to be reversible. The reverse reaction is probably an intermediate step in the synthesis of liver glycogen from glucose in vivo.