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Glucose-6-phosphate dehydrogenase

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Glucose-6-phosphate dehydrogenase (G6PD or G6PDH) (EC 1.1.1.49) is an cytosolic enzyme that catalyzes the chemical reaction

D-glucose 6-phosphate + NADP+ \rightleftharpoons 6-phospho-D-glucono-1,5-lactone + NADPH + H+

This enzyme is in the pentose phosphate pathway (see image), a metabolic pathway that supplies reducing energy to cells (such as erythrocytes) by maintaining the level of the co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH). The NADPH in turn maintains the level of glutathione in these cells that helps protect the red blood cells against oxidative damage. Of greater quantitative importance is the production of NADPH for tissues actively engaged in biosynthesis of fatty acids and/or isoprenoids, such as the liver, mammary glands, adipose tissue, and the adrenal glands. G6PD reduces nicotinamide adenine dinucleotide phosphate (NADP) to NADPH while oxidizing glucose-6-phosphate.[1]

It is notable in humans when there is a genetic deficiency of G6PD which predisposes to non-immune Template:SWL.

Species distribution Edit

G6PD is widely distributed in many species from bacteria to humans. In higher plants, several isoforms of G6PDH have been reported, which are localized in the cytosol, the plastidic stroma, and peroxisomes.[2]

Regulation Edit

Glucose-6-phosphate dehydrogenase is stimulated by its substrate Glucose 6 Phosphate. The usual ratio of NADPH/NADP+ in the cytosol of tissues engaged in biosyntheses is about 100/1. Increased utilization of NADPH for fatty acid biosynthesis will dramatically increase the level of NADP+, thus stimulating G6PD to produce more NADPH.

G6PD converts glucose-6-phosphate into 6-phosphoglucono-δ-lactone and is the rate-limiting enzyme of the pentose phosphate pathway.

G6PD is one of a number of glycolytic enzymes activated by the transcription factor Hypoxia-inducible factor 1 (HIF1).[3]

Clinical significance Edit

G6PD is remarkable for its genetic diversity. Many variants of G6PD, mostly produced from missense mutations, have been described with wide ranging levels of enzyme activity and associated clinical symptoms. Two transcript variants encoding different isoforms have been found for this gene.[4]

Glucose-6-phosphate dehydrogenase deficiency is very common worldwide, and causes acute hemolytic anemia in the presence of simple infection, ingestion of fava beans, or reaction with certain medicines, antibiotics, antipyretics, and antimalarials.[5]

Cell growth and proliferation are affected by G6PD.[6] G6PD inhibitors are under investigation to treat cancers and other conditions.[3] DHEA is a G6PD inhibitor.[6]

See also Edit

References Edit

  1. Aster J, Kumar V, Robbins SL, Abbas AK, Fausto N, Cotran RS (2010). Robbins and Cotran pathologic basis of disease, Kindle Locations 33340–33341, Saunders/Elsevier.
  2. Corpas FJ, Barroso JB, Sandalio LM, Distefano S, Palma JM, Lupiáñez JA, Del Río LA (March 1998). A dehydrogenase-mediated recycling system of NADPH in plant peroxisomes. Biochem. J. 330 ( Pt 2) (Pt 2): 777–84.
  3. 3.0 3.1 de Lartigue J. Cancer Research Moves Beyond the Original Hallmarks of Cancer. OncLive.
  4. Entrez Gene: G6PD glucose-6-phosphate dehydrogenase.
  5. Cappellini MD, Fiorelli G (January 2008). Glucose-6-phosphate dehydrogenase deficiency. Lancet 371 (9606): 64–74.
  6. 6.0 6.1 Tian WN, Braunstein LD, Pang J, Stuhlmeier KM, Xi QC, Tian X, Stanton RC (April 1998). Importance of glucose-6-phosphate dehydrogenase activity for cell growth. J. Biol. Chem. 273 (17): 10609–17.

Further readingEdit

  • Vulliamy T, Beutler E, Luzzatto L (1993). Variants of glucose-6-phosphate dehydrogenase are due to missense mutations spread throughout the coding region of the gene. Hum. Mutat. 2 (3): 159–67.
  • Mason PJ (1996). New insights into G6PD deficiency. Br. J. Haematol. 94 (4): 585–91.
  • Wajcman H, Galactéros F (2004). [Glucose 6-phosphate dehydrogenase deficiency: a protection against malaria and a risk for hemolytic accidents]. C. R. Biol. 327 (8): 711–20.


External links Edit

Template:PDB Gallery Template:Alcohol oxidoreductases Template:Pentose phosphate pathway

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