Duodenal cytochrome B (Dcytb) also known as cytochrome b reductase 1 is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

that in humans is encoded by the

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

. Dcytb CYBRD1 was first identified as a ferric reductase

which catalyzes the reduction of Fe³⁺ to Fe²⁺ required for dietary iron absorption in the

duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...

of mammals. 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. DCYTB protein has also been found in other tissues, such as lung epithelial cells and in the

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

membrane of mature red blood cells of scorbutic species (unable to make ascorbate) such as human and guinea pig 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. 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.

References

External links

* {{Iron metabolism Physiology Enzymes