Glycogenolysis/Glycogenesis

Glycogenolysis

Breakdown of cellular glycogen to G1P

Glycogenesis

Synthesis of Glycogen

Glycogen Phosphorylase

Breakdown glycogen into G1P and new nonreducing end of glycogen

Debranching Enzyme

Has 2 steps

Step 1 of Debranching Enzyme

When there are 4 residues left in a (alpha 1-6) branch, it transfers 3 of those residues to main chain

Step 2 of Debranching Enzyme

Then, it hydrolyzes the single glucose unit that is left at the branch point, releasing it as free glucose

Phosphoglucomutase

Converts G1P → G6P & vice versa. Acts as a switch between glycogenolysis and glycogenesis

G1P & G6P

G1P can then enter glycogenesis and G6P can enter glycolysis

In Muscle

G1P → G6P (phosphoglucomutase), which will enter glycolysis

In ER of Liver Cells

G1P → Glucose (G6Pase) to replenish blood glucose

Glucagon → Glycogen Breakdown

High glucagon → high cAMP → high PKA → high phosphorylase kinase → high glycogen phosphorylase → glycogen breakdown