Glucose-6-phosphate dehydrogenase (G6PD) is a cytosolic enzyme 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.
It is notable in humans when there is a genetic deficiency which predisposes to non-immune haemolytic anaemia.
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Species distribution
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.[1]
Regulation
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.
Clinical significance
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.[2]
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, AAA, antibiotics, antipyretics, and antimalarials.[3]
See also
References
- ^ Corpas FJ et al. (1998). "A dehydrogenase-mediated recycling system of NADPH in plant peroxisomes". Biochem. J.. 330 (7): 777–784.
- ^ "Entrez Gene: G6PD glucose-6-phosphate dehydrogenase". http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=2539.
- ^ Cappellini MD, Fiorelli G (January 2008). "Glucose-6-phosphate dehydrogenase deficiency". Lancet 371 (9606): 64–74. doi:. PMID 18177777.
Further reading
- 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. doi:. PMID 8364584.
- Mason PJ (1996). "New insights into G6PD deficiency.". Br. J. Haematol. 94 (4): 585–91. PMID 8826878.
- 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. PMID 15506519.
External links
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