Pentose Phosphate Pathway

1. Introduction

• Also called as Hexose Monophosphate (HMP) Pathway or shunt and Phophogluconate Pathway
• It is an alternative pathway to glycolysis and TCA cycle for the oxidation of glucose
• The enzymes required for the pathway are located in cytosol of cells of liver, adipose tissue, adrenal gland, erythrocyte, testes, mammary gland etc
• It is an anabolic pathway which leads to many specialized products needed by the cell

2. Two phases of PPP

Phase 1 Oxidative phase

In this phase, glucose 6-phosphate is converted into ribose 5-phosphate

Phase 2 Non-oxidative phase

In this phase, ribose 5-phosphate is again converted back into glucose 6-phosphate

3. Significance of PPP

• Ribose is required for the synthesis of nucleotide and nucleic acids.
• NADPH is required for:
• Synthesis of fatty acids and steroids.
• Counteracting the damaging effects of oxygen free radicals
• In erythrocytes, produced NADPH causes reduction of GSH (glutathione). The reduced GSH removes H2O2 (accumulation of which may cause oxidative damage to the cell membrane, leading to hemolysis).