The Entner-Doudoroff pathway catabolizes glucose to pyruvate using enzymes distinct from glycolysis. It involves the oxidation of glucose-6-phosphate to 6-phosphogluconolactone, followed by dehydration to 2-keto-3-deoxy-6-phosphogluconate and cleavage to pyruvate and glyceraldehyde-3-phosphate. This pathway yields 1 ATP, 1 NADH, and 1 NADPH per glucose, compared to 2 ATP and 2 NADH for glycolysis. It is found in some gram-negative bacteria that lack glycolytic enzymes.

1. Guided By:-Dr. Sunita Satpathy
Presented By:- Ranjita Nayak
Regd.no. :-220705180076
Branch:- Dept. Of M.Sc. Zoology
Course Name:-Molecular Biology (CUTM1436)
School:-School of Applied Science

2. • Introduction
• Phosphorylation
• Oxidative Phase
• Dehydration
• Cleavage Of KDPG
• Oxidation & Phosphorylation
• Substrate Level Phosphorylation
• Isomerization
• Dehydration
• Substrate Level Phosphorylation
• Discussion
• Conclusion
• References
Contents

3. Introduction
The ED pathway was first reported by Michael Doudoroff in Prokaryotic organisms.
The Entner–Doudoroff pathway (ED pathway) catabolizes glucose to pyruvic acid
using enzymes distinct either from those used in glycolysis.
This pathway Uses 6-phosphogluconate dehydratase and 2-keto-3-deoxy
phosphogluconate aldolase to create pyruvate from glucose. The Entner–Doudoroff
pathway also has a net yield of 1 ATP for every glucose molecule processed, as well as
1 NADH and 1 NADPH.
By comparison, glycolysis has a net yield of 2 ATP and 2 NADH for every one glucose
molecule processed.
This pathway is generally found in Pseudomonas, Rhizobium, Azotobacter and
Agrobacterium, and a few other Gram-negative genera. Very few Gram-positive
bacteria have this pathway, with Enterococcus faecalis being a rare exception.
All these bacteria lack enzyme essential for glycolysis, such as phosphofructokinase.
(Kersters, K. 1968)

4. Step 1: Phosphorylation
 Glucose is converted in to glucose 6 phosphate
by Hexokinase enzyme. This is an irreversible
reaction which requires ATP and Atomic
magnesium (Mg++) is also involved.
Step 2: Oxidation of Glucose 6 phosphate to
6-phosphogluconolactone
 This phase starts with the oxidation of 6
molecules glucose 6- phosphate by the enzyme
glucose 6-phosphate dehydrogenase to yield 6-
phosphogluconolactone.
 This enzyme is an NADP dependent enzyme,
where NADP+ reduced to NADPH + H+.
Step 3: Dehydration
 6-phosphogluconate is dehydrated to form 2
keto 3-Doxy-6- phosphogluconate or KDPG.
The key intermediate in this pathway in the
presence of 6-phosphogluconate dehydratase.

5.  Step 4: Cleavage of KDPG
 2 keto 3-Doxy-6-phosphogluconate is then cleaved by
aldolase enzyme to pyruvate and glyceraldehyde 3-
phosphate. The glyceraldehyde 3-phosphateis converted
to pyruvate similar to the reactions of the glycolytic
pathway.
 Step 5: oxidation and Phosphorylation
 In this step, two main events take place: Glyceraldehyde-
3-phosphate is oxidized by the coenzyme nicotinamide
adenine dinucleotide (NAD+);
 The molecule is phosphorylated by the addition of a free
phosphate group result in the formation of 1,3-
bisphosphoglycerate. The enzyme that catalyzes this
reaction is glyceraldehyde-3-phosphate dehydrogenase.
 Step 6: Substrate level phosphorylation
 In this step, 1,3 bisphoglycerate is converted to 3-
phosphoglycerate by the enzyme phosphoglycerate
kinase (PGK).
 This reaction involves the loss of a phosphate group, it
transferred to a molecule of ADP that result in the
formation of ATPs.

6. Step 7: Isomerization
 The 3-phosphoglyceric acid undergoes internal
rearrangement to form 2-phosphoglyceric acid.
 The enzyme phosphoglycero mutase relocates the
phosphate group from the 3rd carbon to the 2nd
carbon to form phosphoglycerate.
Step 8: Dehydration
 this step involves the conversion of 2
phosphoglycerate to phosphoenolpyruvate
(PEP).The reaction is catalyzed by the enzyme
enolase.
 Enolase works by removing a water group, or
dehydrating the phosphoglycerate.
Step 9: Substrate level phosphorylation
 The final step of glycolysis converts
phosphoenolpyruvate into pyruvate with the help
of the enzyme pyruvate kinase.
 The phosphate group attached to the 2′ carbon of
the PEP is transferred to a molecule of ADP,
yielding ATP. Again, since there are one molecules
of PEP, here we actually generate ATP molecules.

7. Has a net yield of 1 ATP for 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
for every one glucose molecule
metabolised.

8. Discussion
• The Entner - Doudoroff pathway begins with the same reactions as the pentose
phosphate pathway, the formation of glucose 6-phosphate and 6-phosphogluconate.
Instead of being further oxidized, 6-phosphogluconate is dehydrated to form 2-keto-3-
deoxy-6-phosphogluconate or KDPG, the key intermediate in this pathway.
• KDPG is then cleaved by KDPG aldolase to pyruvate and glyceraldehyde 3-phosphate.
The glyceraldehyde 3-phosphate is converted to pyruvate in the bottom portion of the
glycolytic pathway.
• If the Entner - Doudoroff pathway degrades glucose to pyruvate in this way, it yields
one ATP, one NADPH, and one NADH per glucose metabolized.

9. Conclusion
• From the above study I conclude that Entner-Doudoroff pathway mainly
found in Gram negative prokaryotes. The end product of this pathway is,
it yield one ATP, one NADPH, and one NADH per glucose metabolized.

10. References
1. Kersters, K., & De Ley, J. (1968). The occurrence of the Entner-Doudoroff pathway in
bacteria. Antonie van Leeuwenhoek, 34, 393-408.
2. Conway, T. (1992). The Entner-Doudoroff pathway: history, physiology and molecular
biology. FEMS microbiology reviews, 9(1), 1-27.
3. Ahmed, H., Ettema, T. J., Tjaden, B., Geerling, A. C., Van Der Oost, J., & Siebers, B.
(2005). The semi-phosphorylative Entner–Doudoroff pathway in hyperthermophilic
archaea: a re-evaluation. Biochemical Journal, 390(2), 529-540.
4. Patra, T., Koley, H., Ramamurthy, T., Ghose, A. C., & Nandy, R. K. (2012). The Entner-
Doudoroff pathway is obligatory for gluconate utilization and contributes to the
pathogenicity of Vibrio cholerae. Journal of bacteriology, 194(13), 3377-3385.
5. Chen, X., Schreiber, K., Appel, J., Makowka, A., Fähnrich, B., Roettger, M., ... &
Gutekunst, K. (2016). The Entner–Doudoroff pathway is an overlooked glycolytic route
in cyanobacteria and plants. Proceedings of the National Academy of Sciences, 113(19),
5441-5446.