Kinetics of dissociation of inactive tetramers of muscle glycogen phosphorylase b into active dimers

Recovery of the enzymatic activity of rabbit skeletal muscle glycogen phosphorylase b preincubated with 1 mM AMP and 0.125 M K2SO4 (0.05 M glycylglycine buffer, pH 6.8; 17 degrees C) has been studied. According to sedimentation data the preincubation conditions favor the formation of the tetrameric form of the enzyme. When registering the kinetics of the enzymatic reaction catalyzed by phosphorylase b preincubated with AMP and K2SO4, an acceleration of the reaction during the course of the enzymatic process was observed. On the basis of the kinetic data the rate constant for dissociation of phosphorylase b tetramers into dimers has been calculated: k=(8.3+/-0.3) 10(-3) sec(-1) (0.05 M glycylglycine buffer, pH 6.8; 17 degrees C).