Navigation Links
Pentose phosphate pathway

The penthose phosphate pathway (also known as the Hexose Monophosphate Shunt) is a process that serves to generate NADPH and the synthesis of pentose (5-carbon) sugars. There are two distinct phases in the pathway. The first is the oxidative phase, in which NADPH is generated, and the second is the non-oxidative synthesis of 5 carbon sugars. The pathway is one of the three main ways the body creates reducing molecules to prevent oxidative stress , accounting for approximately 10% of NADPH production in humans.


Oxidative phase

In this phase, two molecules of NADPH+ are reduced to NADPH, utilising the energy from the conversion of glucose 6-phosphate into ribose 5-phosphate.

The overall reaction for this process is:
Glucose 6-phosphate + 2 NADPH+ + H2O → ribose 5-phosphate + 2 NADPH + 2 H+ + CO2

The first step in this series of reactions is the dehydrogenation of glucose 6-phosphate into 6-phosphoglucono-δ-lactone. This reaction is catalyzed by glucose 6-phosphate dehydrogenase. The hydroxyl group located on carbon 1 of glucose 6-phosphate is converted into a keto group, and in the process, NADPH is generated.

The second step is the hydrolysis of 6-phosphoglucono-δ-lactone to 6-phosphogluconate, which is catalyzed by a lactonase.

The third step is the oxidative decarboxylation of 6-phosphogluconate to ribulose 5-phosphate. This reaction is catalyzed by 6-phosphogluconate dehydrogenase and NADP+ is the electron acceptor, generating another molecule of NADPH.

The final step is the isomerization (catalyzed by phosphopentose isomerase) of ribulose 5-phosphate into ribose 5-phosphate.

The entire set of reactions can be summarized as follows:

  1. Glucose 6-phosphate + NADP+ → 6-phosphoglucono-δ-lactone + NADPH
  2. 6-phosphoglucono-δ-lactone + H2O → 6-phosphogluconate + H+
  3. 6-phosphogluconate + NADP+ → ribulose 5-phosphate + NADPH + CO2

Synthesis of sugar

Non-oxidative phase

  1. ribulose 5-phosphate → ribose 5-phosphate (phosphopentose isomerase)
  2. ribulose 5-phosphate → xylulose 5-phosphate (phosphopentose epimerase)
  3. xylulose 5-phosphate + ribose 5-phosphate → glyceraldehyde 3-phosphate + Sedoheptulose 7-phosphate (transketolase)
  4. sedoheptulose 7-phosphate + glyceraldehyde 3-phosphate → erythrose 4-phosphate + fructose 6-phosphate (transaldolase)
  5. xylulose 5-phosphate + erythrose 4-phosphate → glyceraldehyde 3-phosphate + fructose 6-phosphate (transaldolase)

See also

  • G6PDH deficiency - A hereditary disease which disrupts the pentose phosphate pathway.
  • RNA


(Date:10/7/2015)... -- --> --> According ... third quarter 2015 amounted to around 960 MSEK. This exceeds ... was communicated 20 August 2015. --> ... a continued growing demand for the company,s products, the revenues ... than during the third quarter. The revenue guidance for 2015 ...
(Date:10/2/2015)... Oct. 02 2015 ... "Enforcing the Law Using Biometrics" report ... has announced the addition of the "Enforcing ... offering. --> Research and Markets ( ... "Enforcing the Law Using Biometrics" report ...
(Date:9/29/2015)... Calif. , Sept. 29, 2015 ... improves employee productivity while also saving energy , ... such as Low Power Active Mode and embedded Fujitsu ... transformation Fujitsu today shows that good ... new and refreshed models to its enterprise desktop and ...
Breaking Biology News(10 mins):
Other biology definition