So glycogen synthase is affected by several kinases and contains different phosphorylating sites. However, two very important kinases that are able to actually turn off glycogen synthase A are protein kinase A and glycogen synthase kinase. Now remember that protein kinase A is actually stimulated by cyclic Amp. So if some type of signal transduction pathway takes place that increases the concentration of cyclic Amp within our cell that in turn stimulates PKA. And one of the target proteins of PKA is glycogen synthase A. So upon the stimulation of PKA that essentially promotes the transformation of glycogen synthase A into glycogen synthase B.