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. While originally thought to be just an alternative to glycolysis (EMP) and the 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. 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, ferns, algae, mosses, and plants. Specifically, there is direct evidence that Hordeum vulgare (barley) uses the Entner–Doudoroff pathway.

Archaeal variations

Archaea have variants of the Entner–Doudoroff Pathway. These variants are called the semiphosphorylative ED (spED) and the nonphosphorylative ED (npED): Genera in which the pathway is prominent include Gram-negative, as listed below, Gram-positive bacteria such as Enterococcus faecalis, as well as several in the Archaea, the second distinct branch of the prokaryotes (and the "third domain of life", after the prokaryotic Eubacteria and the eukaryotes). Due to the low energy yield of the ED pathway, anaerobic bacteria seem to mainly use glycolysis while aerobic and facultative anaerobes are more likely to have the ED pathway. This is thought to be due to the fact that aerobic and facultative anaerobes have other non-glycolytic pathways for creating ATP such as oxidative phosphorylation. Thus, the ED pathway is favored due to the lesser amounts of proteins required. While anaerobic bacteria must rely on the glycolysis pathway to create a greater percentage of their required ATP; thus, its 2 ATP production is more favored over the ED pathway's 1 ATP production. a genus of Gram-negative bacteria

  • Rhizobium, a plant root-associated and plant differentiation-active genus of Gram-negative bacteria
  • Agrobacterium, a plant pathogen (oncogenic) genus of Gram-negative bacteria, also of biotechnologic use
  • Escherichia coli, a Gram-negative bacterium
  • Enterococcus faecalis, a Gram-positive bacterium
  • Zymomonas mobilis, a Gram-negative facultative anaerobe
  • Xanthomonas campestris, a Gram-negative bacterium which uses this pathway as main pathway for providing energy.

To date, there is evidence of Eukaryotes using the pathway, suggesting it may be more widespread than previously thought:

  • Hordeum vulgare, barley uses the Entner–Duodoroff pathway.

The Entner–Doudoroff pathway is present in many species of Archaea (caveat, see following), whose metabolisms "resemble... in [their] complexity those of Bacteria and lower Eukarya", and often include both this pathway and the Embden–Meyerhof–Parnas pathway of glycolysis, except most often as unique, modified variants.