Glycogenin is the initiator of the glycogen biosynthesis. This protein is a glycosyl transferase  that have the ability of autoglycosilation using UDP-glucose, which helps in the growth of itself until forming an oligosaccharide made by 8 glucoses. Glycogenin is an oligomer, and it's capable of interacting with several proteins. In recent years, a family of proteins has been identified, the GNIPs (glycogenin-interacting protein), that interacts with glycogenin stimulating its autoglycolsilation activity.