Pentose Phosphate Pathway Flashcards
Production of important intermediates
Produces NADPH ➡️ provides electrons for:
- FA and steroid biosynthesis
- Reduction of glutathione
- Cytochrome P450
- WBC respiratory burst
- Nitric oxide synthesis
Pentose phosphate pathway
Produces ribose-5-phosphate used for synthesis of nucleotides
Metabolic use of 5-carbon sugars
Pentose phosphate pathway
Where does it occur?
In the cytoplasm
What are the substrates?
Glucose-6-phosphate
No consumption or production of ATP
What are the products?
Ribose-5-phosphate, fructose-6-phosphate and glyceraldehyde-3-phosphate
NADPH
Which step is rate-limiting?
Reaction: glucose-6-phosphate ➡️ 6-phosphogluconate
Enzyme: glucose-6-phosphate dehydrogenase
Rescued glutathione (G-SH) removes H2O2 in a reaction catalyzed by glutathione peroxidase
Reacting with H2O2 oxidizes glutathione (G-S-S-G) but only ONLY REDUCED glutathione can remove H2O2
Very important in RBCs
Glutathione
Most common disease producing enzyme abnormality in humans
Involves ⬇️ NADPH in RBCs and ⬇️ activity of glutathione Reductase causing free radicals and peroxides to accumulate
Hemolytic anemia due to poor RBC defense against oxidizing agents
Precipitating factors:
- Most common: infection
- Drugs: AAA: antibiotics (sulfonamides, chloramphenicol), antimalarials (primaquine), antipyretics (except ASA and paracetamol)
- Fave beans
Neonatal jaundice: 1-4 days after birth
HEINZ BODIES: altered hemoglobin that precipitates within RBCs; bite cells- altered RBCs due to phagocytic removal of Heinz bodies in spleen
Glucose-6-phosphate dehydrogenase deficiency
Deficiency in NADPH oxidase
- converts molecular oxygen into superoxide in Leukocytes (especially neutrophils and macrophages) used in the respiratory burst that kills bacteria
Severe, persistent and chronic pyogenic infections caused by catalase positive bacteria
Chronic Granulomatous disease
