[2] In its asymmetric form, glycogen synthase is found as a dimer, whose monomers are composed of two Rossmann-fold domains.

This structural property, among others, is shared with related enzymes, such as glycogen phosphorylase and other glycosyltransferases of the GT-B superfamily.

[3] Nonetheless, a more recent characterization of the Saccharomyces cerevisiae (yeast) glycogen synthase crystal structure reveals that the dimers may actually interact to form a tetramer.

The first family (GT3), which is from mammals and yeast, is approximately 80 kDa, uses UDP-glucose as a sugar donor, and is regulated by phosphorylation and ligand binding.

This suggests that glycogen synthase plays an important biological role in regulating glycogen/glucose levels and is activated by dephosphorylation.

[11] Meanwhile, the muscle isozyme plays a major role in the cellular response to long-term adaptation to hypoxia.

The inactivating phosphorylation is triggered by the hormone glucagon, which is secreted by the pancreas in response to decreased blood glucose levels.

[19] In humans, defects in the tight control of glucose uptake and utilization are also associated with diabetes and hyperglycemia.