EXAM3_L34_Hexose_Monophosphate_Shunt_PPP Flashcards
What are the required enzymes for oxidative HMP
G6PD (rate limiting)
What enzyme and coenzyme required for HMP non-oxidative forward and reverse reactions?
Transketolase (req. TPP)
Forward non-oxidative branch: reactants and products
Ribose5P –> Fructose 6P and Glyceraldehyde3P
Reverse non-oxidative branch reactants and products?
Fructose 6p and glyceraldehyde3p»_space; ribose 5p
How is oxidative HMP regulated?
+ means “activated by”
- means “inhibited by”
+ G6P
+NADP+
- NADPH
How is non-oxidative HMP regulated?
Its not! — some influence by TPP (co-enzyme required by Transketolase)
What is the purpose of Oxidative HMP?
Makes 4 things:
NSFG
- FA synthesis (liver, adipose, lactating gland)
- Steroid Synth (testes, ovaries, placenta, adrenal ctx)
- Glutathione reduction in RBC’s (antioxidant)
- Ribose5P required for nucleotide synthesis
What is the purpose of non-oxidative HMP?
When body doesn’t need Ribose5P they can be converted and fully oxidized for energy
- Allows Metabolism of dietary 5-carbon sugars
What effect does Citrate in the cytosol have on HMP shunt?
Citrate inhibits PFK1 (glycolysis stops)
G6P builds up and enters HMP> increases NADPH >
- FA synthesis or Glutathione reduction or other anabolic processes
Citrate X PFK1 = G6P>HMP>NADPH>FA
What are the two sources of NADPH?
Malic enzyme + Oxidative HMP
The RBC, Cornea, and Lens are tissues without mitochondria. Where do they get NADPH from?
Oxidative HMP only!
Glutathione
Tripeptide with SH group that donates electrons to H2O2
oxidized glutathione is reduced again by NADPH
glutathione synthesis requires ATP
What are the 3 major dietary sources of Fructose?
- Sucrose (glucose + fructose)
- Free fructose (fruits and honey
- High fructose corn syrup (many prepared foods)
Fructose can enter the cells regardless of insulin levels what else makes it unique from glucose?
Extremely poor illicitor of insulin secretion
Why if high fructose SO FATTY!
Fructose enters glycolysis downstream of the PFK1 regulation. (as glyceraldehyde 3 phosphate)
Fructose»_space; DHAP + Glyceraldehyde
- Fructose Metabolism is FASTER
- DHAP can be converted to Glycerol3P (TAG synth)
- Rapid metabolism increases Acetyl-CoA in cytosol (activating FA synth)
