Talk:Pentose phosphate pathway

Errors

For the non-oxidative phase, the diagram, ribose-5-phosphate: on the left it shows a C with a double-bond to an O, and a single-bond to another O. Comparing this to the article for the molecule, the single-bond O seems so be an error. Also in the diagram, this molecule have 9 oxygen atoms, while ribulose- and xyulose-5-phosphate only have 8. Is this really an error? 130.226.87.165 (talk) 14:09, 31 January 2011 (UTC)

In the oxidatice pathway, there should not leave H+ otherwise there is a lack of H+ in the last (oxidation) step on the first carbon that expells carbon dioxide. — Preceding unsigned comment added by 89.102.87.33 (talk) 10:40, 25 January 2014 (UTC)

Regulation

The sentence "Glucose-6-phosphate dehydrogenase is the rate-controlling enzyme of this pathway." is incorrect and should be deleted. Rate limitation is dependent on the state of the cell, and so even if under certain conditions this enzyme could hold a considerable level of control, in many other conditions this control will shift to other steps. There is not single "rate-controlling" enzyme in any pathway, as has been shown, eg in the field of Metabolic control analysis. If the sentence is to be allowed here at least it requires a reference! — Preceding unsigned comment added by 68.199.68.103 (talk) 20:43, 13 July 2011 (UTC)

General Comments

Overview: When discussing the products generated it should state that the products are generated from the oxidation of glucose-6-phosphate. Additionally, it should specifically state what the conditions of the Archaen ocean that allow for the non-enzymatic pathway.

Outcomes In the aromatic amino acids portion the reference to lignin in wood is unnecessary, irrelevant, and it is unclear what pathway biosynthetic pathway lignin is a precursor for.

A citation would be useful for the dietary pentose portion. The overall lack of citations is really damaging the reliability of the page.

For the portion on mammals there is a typo: "in the human" should be "in humans". Potential citation for this portion is Lehninger Principles of Biochemistry.

Regulation the sentence: "Glucose-6-phosphate dehydrogenase is the rate-controlling enzyme of this pathway" is misleading. The pathway is inhibited by NADPH and the ratio of NADPH:NADP+ is what determines flux, not the enzyme itself. Anhill95 (talk) 05:03, 17 March 2017 (UTC)

Comments

In the last line of the first section the word choice "This suggests" does not seem appropriate as it seems like its the authors opinion. Rather it would be better to have a citation that could suggest that the origin of the pentose phosphate pathway could have had its roots in the prebiotic world.

In the outcome section of the article many statements are being made but they are not supported by citations. The information about aromatic amino acids or the last line about hydrogen peroxide don't add any weight in the section and can be removed.

For the regulation section, while there was a mention Glucose-6-phosphate dehydrogenase being allosterically controlled enzyme, I do agree with the above comment about "Glucose-6-phosphate dehydrogenase is the rate-controlling enzyme of this pathway" being misleading. It would be better to rephrase the statement and add a citation as well.

Over all the article lacks citations which would add more credibility to the article. Majumak (talk) 06:08, 18 March 2017 (UTC)

Comments/Citations

In the outcome section, there needs to be a lot more citations. There is only one citation for the whole section, when you make a multitude of claims. Also the sentences need to be edited a little bit more. Instead of "in the human." it should just be "in humans". Also you never abbreviated the pentose phosphate pathway as the PPP, so you should put (PPP) when you first write the pentose phosphate pathway so that the reader knows that that is what PPP means. Also you should clarify what molecules with reducing power is and what that means as well as its importance in metabolism.

In the phases section, you should add free energy as well as if the steps are irreversible or reversible. The non-oxidative phase could be better explained (more sentences than tables) Also the net reaction could be easier to read. You also need more citations on regulation. You say that the ratio of NADPH:NADP+ is about 100:1 in liver cytosol. Where did you get this info? Is it the same in all livers of all animals? or a certain animal?

Geowong (talk) 17:59, 18 March 2017 (UTC)

Comments and Concerns

Outcome section is helpful but needs citations and includes some non-essential, distracting information.

Phases is organized nicely with good diagrams, but in need of citations.

The citations are from reputable, un-biased sources (peer reviewed journals). The links seems to be working.

This is article is fairly short. Perhaps an additional section could be added about differences/similarities of PPP in various organisms.

Katiemcpherson (talk) 22:23, 20 March 2017 (UTC)