GLYCOGEN METABOLISM

Lourdes L. Balcueva,M.D.

Glycogen Metabolism

• - Glycogen is the main storage form of glucose in animals; starch in plants - Occurs in all tissues but predominantly in the liver and muscles - Muscle glycogen- provides glucose (glucose 6-PO4) for glycolysis - Liver glycogen- provides glucose to maintain blood glucose level

Glycogenesis

- substrate for polymerization are sugar nucleotides (UDPGlc)- enzymes involved: 1. Glucokinase (Hexokinase) Glucose Glucose 6-PO4

Glycogenesis

2. Phosphoglucomutase Glucose 6-PO4 Glucose 1-PO4

3. UDPGlc pyrophsphorylase Glucose 1-PO4 + UTP UDPGlc + PPi

4. Pyrophosphatase PPi 2 Pi

Glycogenesis

• 5. Glycogen Synthase

UDPGlc Glycogen primer + UDP

(14 linkage)

6. Branching Enzyme

transfers 6 glucose residues from 11

existing (14 chain) to form 16

linkage

GLYCOGENOLYSISEnzymes involved:1. Glycogen phosphorylase: phosphorylytic cleavage of glycogen (14 linkage) to Glucose 1- PO4 2. Glucan transferase: transfers 3 units of 1glycogen to another exposing the glycogen with 16 linkage

Glycogenolysis3. Debranching Enzyme: hydrolysis of glycogen at 1branching as free glucose molecule 4. Phosphoglucomutase – reversible Glucose 1-P Glucose 6-P 5. Glucose 6-phosphatase (liver and kidney) Glucose 6-P Glucose

• THANK YOU