The accepted name varies according to the source of the enzyme and the nature of its synthetic product (cf. EC 2.4.1.1, phosphorylase). Glycogen synthase from animal tissues is a complex of a catalytic subunit and the protein glycogenin. The enzyme requires glucosylated glycogenin as a primer; this is the reaction product of EC 2.4.1.186 (glycogenin glucosyltransferase). A similar enzyme utilizes ADP-glucose (EC 2.4.1.21, starch synthase).
