5P Steps
Pentose Phosphate Pathway
Pentose Phosphate Steps:
Oxidative
- G6P into 6PGdL - Glucose 6-phosphate dehydrogenase (G6PDH)
- Glucose 6-phosphate into 6-phosphoglucono-delta-lactone
- 6PGdL into 6PGate - Lactonase
- 6-phosphoglucono-delta-lactone into 6-phosphogluconate
- 6PGate into Ru5Pate - 6-phosphogluconate dehydrogenase (6PGDH)
- 6-phosphogluconate into Ribulose 5-phosphate
- Two molecules of NADPH are generated in the conversion
Nonxidative
- Ribulose 5-phosphate can have 2 fates:
- 1)Ru5P into Ro5P - Phosphopentose isomerase (5PIs)
- Ribulose 5-phosphate into Ribose 5-phosphate
- 2)Ru5P into X5P - Phosphopentose epimerase (5PEp)
- Ribulose 5-phosphate into Xylulose 5-phosphate
- Additional Steps Considered With Ro5P Focus
Focus on Ribose 5-phosphate
- Ro5P or X5P <-- Ru5P
- Ribose 5-phosphate is a precursor to many biomolecules
- Many cells need NADPH for reductive biosynthesis more than Ribose 5-phosphate
- Incorporation into nucleotides and nucleic acids
- Adipose tissue the liver and mammary glands require large amounts of NADPH for tatty acid synthesis
- Summary:
- Ro5P into GAP and F6P - Transketolase and Transaldolase
- Ribose 5-phosphate into Glyceraldehyde 3-phosphate and Fructose 6-phosphate
- REVERSIBLE link between 5PP and Glycolysis/Gluconeogenesis
- Formation of two hexoses and one triose from these pentoses
- Specifics:
- 1)Xu5P + Ro5P into GAP and S7P - Transketolase
- Xylulose 5-phosphate and Ribose 5-phosphate into Glyceraldehyde 3-phosphate and Sedoheltulose 7-phosphate
- Xu5P is the donor
- 2)GAP + S7P into F6P + E4P - Transaldolase
- Glyceraldehyde 3-phosphate and Sedoheltulose 7-phosphate into Fructose 6-phosphate and Erythrose 4-phosphate
- 3)E4P + Xu5P into F6P + GAP - Transketolase
- Erythrose 4-phosphate and and Xylulose 5-phosphate (From R5P) into Fructose 6-phosphate and Glyceraldehyde 3-phosphate
