Dr.Qball

2+ Year Member
Jul 19, 2016
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Hello everyone, I am sorry if I am posting in the wrong thread because this is my first time posting on this page. I just had a question regarding the Pentose Phosphate Pathway (PPP).

I believe I read some conflicting information on the PPP and am very confused. I was going over the Kaplan MCAT quick sheet and read that glucose-6-phosphate dehydrogenase (G6PD) is activated by NADP+ and inhibited by NADPH and Insulin. I was confused so I went to read the book and then it said PPP G6PD is induced by insulin because...... I thought high insulin levels would mean the PPP would go faster because there is suffient energy for the cell to make DNA, RNA intermediates. Can some please clarify this for me.

Thank you!
 

theonlytycrane

5+ Year Member
Mar 23, 2014
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On my quicksheet it says: it's activated by NADP+ and insulin and inhibited by NADPH.
 

theonlytycrane

5+ Year Member
Mar 23, 2014
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+ by insulin would make sense. Cells take in glucose, increasing g6p availability for p3.
 

mw18

5+ Year Member
Jan 7, 2014
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It is induced by insulin, because glucagon would tell it to save its glucose. Which would inhibit the pathway. If glucagon stops it, then insulin starts it.
 
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Dr.Qball

2+ Year Member
Jul 19, 2016
47
12
It makes sense that insulin does activate the PPP. I guess it is just a typo on the Kaplan MCAT quick sheet because the Kaplan Biochemisry Book does say insulin induces it so thank you everyone for the reply!
 

wizzed101

The Little Prince
May 20, 2016
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Interesting. I also found papers stating that the effects of insulin were tissue dependent.
Ex:
http://www.jbc.org/content/273/24/14968.long
The whole paper was about how insulin upregulated a particular cell type in fruit flies. One would think that this is trivial.
http://www.ncbi.nlm.nih.gov/pubmed/14644433

Only the older papers claimed that insulin upregulated PPP, universally...

Newer ones kinda imply the opposite:
http://www.ncbi.nlm.nih.gov/pubmed/22682085
http://www.ncbi.nlm.nih.gov/pubmed/23015612
-> insulin resistance lead to activation of G6PD, and more NADPH -> beneficial
 

mw18

5+ Year Member
Jan 7, 2014
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Interesting. I also found papers stating that the effects of insulin were tissue dependent.
Ex:
http://www.jbc.org/content/273/24/14968.long
The whole paper was about how insulin upregulated a particular cell type in fruit flies. One would think that this is trivial.
http://www.ncbi.nlm.nih.gov/pubmed/14644433

Only the older papers claimed that insulin upregulated PPP, universally...

Newer ones kinda imply the opposite:
http://www.ncbi.nlm.nih.gov/pubmed/22682085
http://www.ncbi.nlm.nih.gov/pubmed/23015612
-> insulin resistance lead to activation of G6PD, and more NADPH -> beneficial
For the mcat I would focus on broad concepts. Insulin leads to taking glucose out of the blood and into the cell and using it. Glucagon wants glucose to stay in glucose form. PPP takes it out of glucose form and leads to its breakdown. So, insulin induces PPP and glucagon does the opposite.