Kahn, V., Department of Physiology and Pharmacology, Duke University Medical Center, Durham, NC 27706, United States
Blum, J.J., Department of Physiology and Pharmacology, Duke University Medical Center, Durham, NC 27706, United States

Glycogen phosphorylase (α-1,4-glucan; orthophosphate glucosytransferase, EC 2.4.1.1) was purified 130-fold from acetone powder prepared from Tetrahymena pyriformis. The most purified preparation was about 40% pure as judged by polyacrylamide disc gel electrophoresis and had a specific activity of 4.1 μmoles Pi/min/mg protein. The enzyme also catalysed the phosphorolysis of glycogen and is thus a true glycogen phosphorylase. The molecular weight of the enzyme was about 200,000 as determined by sucrose density gradient centrifugation, but two peaks, corresponding to molecular weights of 100,000 and 200,000 were observed on Sephadex G-200 gel chromatography. The enzyme was slowly inactivated at temperatures up to 50 ° but a sharp increase in the rate of inactivation occurred above 50 °. AMP, but not glucose-1-phosphate or glycogen, partially protected the enzyme against thermal inactivation. AMP and structurally related nucleoside monophosphates neither stimulated nor inhibited the activity of the enzyme. © 1971.