Insoluble glycogen and its interaction with phosphorylase. A novel method for the purification of liver phosphorylase A

Abstract

Purified liver glycogen dissolved in Tris-HCl buffer (pH 6.8) was converted into an insoluble polymer by incubation with phosphorylase and glucose 1-phosphate. Elongation of the outer chains of glycogen did not alter the average molecular weight significantly as judged by sedimentation velocity measurements, but the spectrophotometric analysis of glycogen-iodine complexes showed marked differences. Insoluble glycogen could bind rabbit skeletal muscle and liver phosphorylases. The association of insoluble glycogen with phosphorylase could be treated as a distribution equilibrium between glycogen-bound and unbound phosphorylase. Based on the formation of an insoluble glycogen protein complex sedimentable even by low-speed centrifugation, a novel method has been developed for the purification of liver phosphorylase a in a homogeneous form.