Inactivation and Activation of Liver Phosphorylase

Abstract

THE level of phosphorylase in liver slices represents a balance between inactivation and resynthesis of the active form; epinephrine and glucagon rapidly increase the amount of active phosphorylase in pre-incubated liver slices^1,2. In order to study the nature of the change in the phosphorylase molecule, liver phosphorylase and the enzyme inactivating it from dog liver have been prepared in purified form. The liver phosphorylase was purified approximately 400-fold, a value higher than previously reported³; this purified enzyme was very soluble in water and when inactivated enzymatically showed little or no activity when tested in the presence of adenylic acid. The inactivating enzyme from dog liver was also purified about 400-fold, and this purified enzyme was sufficiently active for microgram quantities to be used in most experiments. Preliminary tests using several proteins as possible substrates have revealed no proteolytic activity.