Pentose Phosphate Pathway (PPP) Flashcards
What is the purpose of the PPP
It generates NADPH and Ribose-5-Phosphate which are used for synthetic reactions in the body, including nucleic acid synthesis.
Also leads to production of sugar intermediates like Ribose-5-phosphate and riulose-5-phosphate that are essential to nucleic acid synthesis
What are the three steps of this reaction?
- Oxidative Reactions
- Isomerization and Epimerization Reactions
- C-C Bond Cleavage and Formation Reactions
What are the enzymes associated with the oxidative reactions?
- Glucose-6-phosphate Dehydrogenase
- 6-Phosphogluconolactonase
- 6-phosphogluconate Dehydrogenase
What are the enzymes associated with the Isomerization and Epimerization reactions?
- Ribulose-5-phosphate isomerase
- Ribulose-5-phosphate epimerase
What are the enzymes associated with the C-C bond cleavage/formation reactions?
- Transketolase
- Transaldolase
How is the PPP regulated?
Glucose 6 Phosphate Dehydrogenase (G6P DH) is the main enzyme that controls the flux (overall rate) of this pathway
What is Glucose6-Phosphate Dehydrogenase (G6P-DH) inhibited by?
It is strongly inhibited by NADPH. If NADPH concentration decreases, G6P-DH is activated.
What is the role of NADPH in reducing oxidative stress?
NADPH is used to generate reduced glutathione (GSH) which plays a major role in quenching the oxyradicals in the cell.
What happens when NADPH generation is inhibited by mutations in the G6P-DH cells?
Cells can become susceptible to oxidative damage.
Why are people with G6P-DH defects immune from malaria?
There are more oxyradicals present in the cell due to the defective G6P-DH inhibiting NADPH production.
The Malaria parasite is extremely sensitive to Oxy-radicals
Because of this, the malaria parasites are killed by the excessive oxy-radicals in the cell.
