Entner–Doudoroff pathway

The Entner–Doudoroff pathway (ED Pathway) is a metabolic pathway that is most notable in Gram-negative bacteria, certain Gram-positive bacteria and archaea. Glucose is the substrate in the ED pathway and through a series of enzyme assisted chemical reactions it is catabolized into pyruvate. Entner and Doudoroff (1952) and MacGee and Doudoroff (1954) first reported the ED pathway in the bacterium Pseudomonas saccharophila. 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 uses the Entner–Doudoroff pathway.

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

• Uses the unique enzymes 6-phosphogluconate dehydratase aldolase and 2-keto-deoxy-6-phosphogluconate (KDPG) aldolase and other common metabolic enzymes to other metabolic pathways to catabolize glucose to pyruvate.
• 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.