Glycogen synthase (UDP-glucose-glycogen glucosyltransferase) is an enzyme involved in converting glucose to glycogen. It takes short polymers of glucose and converts them into long polymers of glycogen.n the other hand, much less is known about the structure of glycogen synthase, the key regulatory enzyme of glycogen synthesis. The crystal structure of glycogen synthase from Agrobacterium tumefaciens, however, has been determined at 2.3 A resolution.