Some properties of a liver protein that activates glycogen synthase b

A soluble protein has been identified in rat liver that increases the activity of glycogen synthase without causing synthase b to a conversion. The effect of the activator is to increase synthase b activity in the presence of saturating amounts of UDP-Glc and Glc-6-P. The activator is heat sensitive and does not have protease activity. The effect of the activator is linearly proportional to the amount assayed to a saturable level and its effect is not mimicked by other proteins associated with the control of glycogen metabolism (e.g., phosphorylase).