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Pentose phosphate pathway (PPP)
- Provides route for metabolism of glucose
- ATP is consumed/produced
- production of reducing power in form of NADPH and ribose
- Location: liver, rbc's, mammary glands, adipose tissue, adrenal cortex
- site: cytosol
- function: generate NADPH for biosynthetic rxns ex: fatty acid/cholesterol synthesis
- production of 5 carbon
- generates ribose 5 phosphate & NADPH for nucleotide biosynthesis. one can get either one, or both.
- regulated by G6PD
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2 Pentose Phosphate Pathways
- 1. Irreversible oxidative.
- 2. Reversible non-oxidative.
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Irreversable oxidative rxns
- 3 rxns
- convert G5P to Ribulose5P w/ release of Co2 and nadph
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PPP in RBC
NADPH used to regenerate the antioxidant glutathione, which protects cells against damage. (keeps glutathione reduced)
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G6PD: glucose-6p-dehydrogenase
- Nadp is it's coenzyme
- Rate limiting enzyme
- converts g6p to 6phos-glu-nolacetone. Final is (ribulose5p)
- inhibited by NADPH
- Ratio of NADPH/NADP is high which inhibits enzyme activity.
- In enhanced activity, ratio decrease, and demand of NADPH goes up.
- 2 nadph for biosynthesis & glutathion (GSH)
- Insulin regulates G6PD, pathway increases in FED state.
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NADPH
- high energy, used for reductive synthetic reaction.
- competitive inhibitor of enzyme G6PD
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GSH
Antioxidant, neutralizes the oxidant activity of H2O2.
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NADH
tranfer electrons to electron transport chain to make ATP
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RIB5P
6phos-glu-nolactone hydrolyzed by 6phos-glu-nolactone Hydrolase
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