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.

Contents

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.
  • NADPH
  • RNA

'"/>


(Date:12/17/2014)... Va. , Dec. 15, 2014 ... to make it easier to detect and prevent ... Today the agency started performing an ... capability will validate the authenticity of purchased microcircuits ... The new quality control measures will be conducted ...
(Date:12/17/2014)... , Dec. 16, 2014  Automation is ... this more evident than at international borders. Over ... document scanners have allowed veteran travelers to self ... Passport Control (APC) Kiosks at an increasing number ... globe. According to Maxine ...
(Date:12/11/2014)... WINSTON SALEM, N.C. , Dec. 10, 2014  That ... known for quite a while. Hypertension – the medical term ... disease in the early 1800s, and the inflatable cuff that,s ... That doesn,t, however, mean there,s nothing new about hypertension, ... punctured some long-held beliefs about the condition and the best ...
Breaking Biology News(10 mins):Defense Logistics Agency Launches DNA Marking Capability to Strengthen Microcircuit Supply Chain 2Defense Logistics Agency Launches DNA Marking Capability to Strengthen Microcircuit Supply Chain 3Automated Border Control (ABC) Transforms the Global Travel Experience With More Than 2500 ABC eGates and APC Kiosks Deployed In Airports, Seaports, and Land Borders Worldwide 2Research points to need for new approaches to treatment of high blood pressure 2Research points to need for new approaches to treatment of high blood pressure 3Research points to need for new approaches to treatment of high blood pressure 4
... of funding-- dollars drop, in this particular case, for ... faculty and staff. Those declines ultimately impact student ... "Obviously if you,ve had a 30% reduction in funding, ... budget. And so programs are affected," says Colorado ...
... − A new study from the Infant Brain Imaging ... Research at the Children,s Hospital of Philadelphia (CHOP), found ... months in high-risk infants who later develop autism, compared ... "It,s a tremendously exciting finding," said Sarah Paterson, PhD, ...
... SEATTLE Evolutionary biologist Harmit Singh Malik, Ph.D., of ... grant from the Lupus Research Institute to study the ... lupus, an autoimmune disease. , Malik and colleagues want ... causes lupus autoimmunity., "We want to determine whether autoimmunity ...
Cached Biology News:New autism research reveals brain differences at 6 months in infants who develop autism 2Did an evolutionary arms race cause lupus? Biologist Harmit Malik receives grant to try and find out 2
Other biology definitionOther Tags