glycogen synthesis

Glucose-1-phosphate

Glycogen degradation yields

UDP-glucose

Monomer used to extend glycogen chain in synthesis

Glycogen (n) + UDP-glucose → glycogen (n+1) + UDP

Glycogen synthesis equation:

Glycogen (n+1) + phosphate → glycogen (n) + glucose-1-phosphate

Glycogen degradation equation:

Glucose-1-phosphate and UTP, producing UDP glucose and pyrophosphate

Uridine diphosphate glucose (UDP-glucose) is formed from

UDP-glucose pyrophosphorylase , reversible

The formation of UDP-glucose is catalyzed by … and is …

Pyrophosphate + h20 → 2 phosphate.

This causes the net reaction to produce 2 phosphates

The part of the UDP-glucose production that is irreversible pushing the reaction forward

10 molecules

To store 1 glucose as glycogen … of water is needed

No reducing terminal residues

New glucosyl units are added to … portions of glycogen

Hydroxyl group at C-4

Alpha-1,4-glycosidic linkage

The activated glucosyl unit of UDP-glucose is transferred to … of the terminal residue within the glycogen chain to form a …

The addition of a glucose to a glycogen chain by UDP-glucose

Glycogen synthase catalyzes:

Liver, muscle & other muscles

Where the 2 isozymic forms of glycogen synthase is located

Already at least 4 residues in length. Therefore glycogen synthesis requires a primer

Glycogen synthase can only add glucosyl residues to polysaccharide chains that are

Glycogenin, a self glucosing enzyme

The primer for glycogen synthase

Formation of alpha-1,4-glucose polymers on its partner subunit. Forming a polymer of 10-20 glucosyl units

Each subunit of Glycogenin catalyzes

Alpha-1,4-linkages

The bond only glycogen synthase catalyzes

It increases solubility and provides more terminal residues which are the sites of action for glycogen phosphorylase and synthase. It increases the rate of synthesis and degradation

Branching is important in glycogen as

Breaking a alpha-1,4 link and transferring it to form the alpha-1,6. branch using branching enzyme

The blocks are usually 7 residues in length moved interiorly from a chain that is at least 11 residues long. A new branch point must be at least 4 residues from a preexisting one.

A alpha-1,6 branch is made through:

Active nonphosphorylated A form

Inactive phosphorylated B form

The two forms of glycogen synthase

Glucose-6-phosphate

Activator of glycogen synthase enzyme

2 ATP

31 ATP

How much ATP used to add dietary glucose to glycogen

How much ATP yielded when oxidating glycogen to glucose

High glucagon and epinephrine inhibits synthesis promoting breakdown

Glycogen synthesis is inhibited by the same signalling pathway that stimulates glycogen breakdown (opposite processes so they are related in reverse)

• activating signal transduction pathways

• Increasing the number of GLUT4

Insulin stimulates glycogen synthesis (a form of uptake) by:

Glycogen phosphorylase

Liver

Glycogen synthase

High blood glucose inhibits glycogen degradation through … in the … and increases glycogen synthesis through …