In glycogenolysis, it is the direct product of the reaction in which glycogen phosphorylase cleaves off a molecule of glucose from a greater glycogen structure.

A deficiency of muscle glycogen phosphorylase is known as glycogen storage disease type V (McArdle Disease).

To be utilized in cellular catabolism it must first be converted to glucose 6-phosphate by the enzyme phosphoglucomutase in a free equilibrium.

[1][2][3] One reason that cells form glucose 1-phosphate instead of glucose during glycogen breakdown is that the very polar phosphorylated glucose cannot leave the cell membrane and so is marked for intracellular catabolism.

Phosphoglucomutase-1 deficiency is known as glycogen storage disease type 14 (GSD XIV).