Glycogenolysis is the breakdown of glycogen (n) to and glycogen (n-1). Glycogen branches are catabolized by the sequential removal of glucose monomers via phosphorolysis, by the enzyme glycogen phosphorylase.
glycogen(n residues) + Pi ⇌ glycogen(n-1 residues) + glucose-1-phosphate
Here, glycogen phosphorylase cleaves the bond linking a terminal glucose residue to a glycogen branch by substitution of a phosphoryl group for the α[1→4] linkage. Glucose-1-phosphate is converted to (which often ends up in glycolysis) by the enzyme phosphoglucomutase.
