Purification and properties of glycogen phosphorylase from Escherichia coli

Abstract Glycogen phosphorylase and maltodextrin phosphorylase were purified 1100-fold and 200-fold respectively from cell-free extracts of Escherichia coli, K-12. The optimum pH of the glycogen phosphorylase is 6.7–6.9 and the equilibrium favors glycogen synthesis from glucose-1-phosphate. The spectrum of the enzyme suggests that it contains pyridoxal phosphate. Heavy metals and pCMB are inhibitory. The Km values for glucose-1-phosphate and glycogen are 10−3 m and 0.67% w v , respectively in the absence of AMP and 2.9 × 10−3 m and 0.46% w v , respectively in the presence of 5 × 10−3 m AMP. AMP increased the Vmax of the reaction slightly when glycogen was not saturating. Glucose (Ki = 2.5 × 10−>m), ADPG (Ki = 0.7 × 10−>m), TDPG (Ki = 10−m), and UDPG (Ki = 2 × 10−m) were competitive inhibitors with respect to glucose-1-phosphate. Glucose-1-phosphate (at > 2 × 10− m ) was also inhibitory.