Editing Entner–Doudoroff pathway (section)

{{Short description|Series of interconnected biochemical reactions}}
[[Image:Entner–Doudoroff pathway.svg|thumb|200px|Diagram of the Entner–Doudoroff pathway (KDPG: 2-keto-3-deoxy-6-phosphogluconate)]]The '''Entner–Doudoroff pathway''' (ED Pathway) is a [[metabolic pathway]] that is most notable in [[Gram-negative bacteria]], certain [[Gram-positive bacteria]] and [[archaea]].<ref name="Conway" /> [[Glucose]] is the substrate in the ED pathway and through a series of [[enzyme]] assisted [[chemical reaction]]s it is catabolized into [[Pyruvic acid|pyruvate]]. Entner and [[Michael Doudoroff|Doudoroff]] (1952) and MacGee and Doudoroff (1954) first reported the ED pathway in the bacterium ''[[Pelomonas saccharophila|Pseudomonas saccharophila]]''.<ref>{{Cite journal|last1=Kersters|first1=K.|last2=De Ley|first2=J.|date=December 1968|title=The occurrence of the Entner-Doudoroff pathway in bacteria|journal=Antonie van Leeuwenhoek|volume=34|issue=1|pages=393–408|doi=10.1007/BF02046462|pmid=5304016|s2cid=6151383|issn=0003-6072}}</ref> While originally thought to be just an alternative to [[glycolysis|glycolysis (EMP)]] and the [[pentose phosphate pathway|pentose phosphate pathway (PPP)]], some studies now suggest that the original role of the EMP may have originally been about [[anabolism]] and repurposed over time to [[catabolism]], meaning the ED pathway may be the older pathway.<ref>{{Cite journal|last1=Romano|first1=A. H.|last2=Conway|first2=T.|date=1996-07-01|title=Evolution of carbohydrate metabolic pathways|journal=Research in Microbiology|volume=147|issue=6|pages=448–455|doi=10.1016/0923-2508(96)83998-2|issn=0923-2508|pmid=9084754|doi-access=free}}</ref> Recent studies have also shown the prevalence of the ED pathway may be more widespread than first predicted with evidence supporting the presence of the pathway in [[cyanobacteria]], [[fern]]s, [[algae]], [[moss]]es, and [[plant]]s.<ref name="Chen 2016">Chen, Xi, et al. "The Entner–Doudoroff pathway is an overlooked glycolytic route in cyanobacteria and plants." ''Proceedings of the National Academy of Sciences'' (2016): 201521916.</ref> Specifically, there is direct evidence that [[Barley|''Hordeum vulgare'']] uses the Entner–Doudoroff pathway.<ref name="Chen 2016" />

Distinct features of the Entner–Doudoroff pathway are that it:

* Uses the unique enzymes 6-phosphogluconate dehydratase and 2-keto-deoxy-6-phosphogluconate (KDPG) aldolase and other common metabolic enzymes to other metabolic pathways to catabolize glucose to pyruvate.<ref name="Conway" />
* In the process of breaking down glucose, a net yield of 1 ATP is formed per every one glucose molecule processed, as well as 1 [[NADH]] and 1 [[NADPH]]. In comparison, glycolysis has a net yield of 2 ATP molecules and 2 NADH molecules per every one glucose molecule metabolized. This difference in energy production may be offset by the difference in protein amount needed per pathway.<ref name=":0">{{Cite journal|last1=Flamholz|first1=A.|last2=Noor|first2=E.|last3=Bar-Even|first3=A.|last4=Liebermeister|first4=W.|last5=Milo|first5=R.|date=2013-04-29|title=Glycolytic strategy as a tradeoff between energy yield and protein cost|journal=Proceedings of the National Academy of Sciences|volume=110|issue=24|pages=10039–10044|doi=10.1073/pnas.1215283110|pmid=23630264|pmc=3683749|bibcode=2013PNAS..11010039F|issn=0027-8424|doi-access=free}}</ref>