Biology:Duodenal cytochrome B
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Duodenal cytochrome B (Dcytb) also known as cytochrome b reductase 1 is an enzyme that in humans is encoded by the CYBRD1 gene.
Dcytb CYBRD1 was first identified as a ferric reductase enzyme which catalyzes the reduction of Fe3+ to Fe2+ required for dietary iron absorption in the duodenum of mammals.[1] Dcytb mRNA and protein levels in the gut are increased by iron deficiency and hypoxia which acts to promote dietary iron absorption. The effect of iron deficiency and hypoxia on Dcytb levels are medicated via the HIF2 (Hypoxia inducible factor 2) transcription factor which binds to hypoxia response elements within the Dcytb promoter and increases transcription of the gene.[2] DCYTB protein has also been found in other tissues, such as lung epithelial cells[3] and in the plasma membrane of mature red blood cells of scorbutic species (unable to make ascorbate) such as human and guinea pig[4] but not in other species which have retained the ability to synthesise ascorbate like mice and rat. This has led to the notion that Dcytb may have an additional role in ascorbate metabolism in scorbutic species. DCYTB protein has also been found in breast tissue (epithelial and myoepithelial cells) and high DCYTB levels are associated with a favourable prognosis in patients with breast cancer.[5] A single nucleotide polymorphism (SNP) within the DCYTB promoter (SNP rs884409) which reduced functional DCYTB promoter activity was also associated with reduced serum ferritin levels in a patient cohort with C282Y haemochromatosis.[6]
References
- ↑ "An iron-regulated ferric reductase associated with the absorption of dietary iron". Science 291 (5509): 1755–9. March 2001. doi:10.1126/science.1057206. PMID 11230685. Bibcode: 2001Sci...291.1755M.
- ↑ "Intestinal hypoxia-inducible transcription factors are essential for iron absorption following iron deficiency". Cell Metabolism 9 (2): 152–64. February 2009. doi:10.1016/j.cmet.2008.12.012. PMID 19147412.
- ↑ "Duodenal cytochrome b: a novel ferrireductase in airway epithelial cells". American Journal of Physiology. Lung Cellular and Molecular Physiology 291 (2): L272–80. August 2006. doi:10.1152/ajplung.00342.2005. PMID 16510471.
- ↑ "Human erythrocyte membranes contain a cytochrome b561 that may be involved in extracellular ascorbate recycling". The Journal of Biological Chemistry 281 (52): 39852–9. December 2006. doi:10.1074/jbc.M606543200. PMID 17068337.
- ↑ "DCYTB is a predictor of outcome in breast cancer that functions via iron-independent mechanisms". Breast Cancer Research 19 (1): 25. March 2017. doi:10.1186/s13058-017-0814-9. PMID 28270217.
- ↑ "A novel association between a SNP in CYBRD1 and serum ferritin levels in a cohort study of HFE hereditary haemochromatosis". British Journal of Haematology 147 (1): 140–9. October 2009. doi:10.1111/j.1365-2141.2009.07843.x. PMID 19673882.
External links
- duodenal+cytochrome+b,+human at the US National Library of Medicine Medical Subject Headings (MeSH)
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