Biotin
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| Biotin | |
| Missing image Biotin.png image:Biotin.png | |
| General | |
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| Chemical formula | C10H16N2O3S |
| Molecular weight | 244.31 g/mol |
| Other names | |
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| Vitamin properties | |
| Solubility | Water |
| RDA (adult male) | 30 μg/day |
| RDA (adult female) | 30 μg/day |
| RDA upper limit (adult male) | None |
| RDA upper limit (adult female) | None |
| Deficiency symptoms | |
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| Excess symptoms | |
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| Common sources | |
Biotin, also known as vitamin H or B7 and C10H16N2O3S (Biotin; Coenzyme R, Biopeiderm), is a water-soluble B-complex vitamin which is important in the catalysis of essential metabolic reactions to synthesize fatty acids, in gluconeogenesis, and to metabolize leucine. It is commonly found in pyruvate dehydrogenase as a carrier of HCO3-</sup>.
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Deficiency
Biotin deficiency rarely occurs in healthy individuals. This is due to the facts that the daily requirements of biotin are low, many foods contain adequate amounts, intestinal bacteria synthesize small amounts, and the body effectively scavenges and recycles biotin from bodily waste. However, deficiency can be caused by excessive consumption of raw egg-whites over a long period (months to years). Egg-whites contain high levels of avidin, a protein that binds biotin stongly. Once cooked, the egg-white avidin becomes denatured and entirely non-toxic.
Biochemistry
Biotin is a cofactor responsible for carbon dioxide transfer in several carboxylase enzymes:
- Acetyl-CoA carboxylase
- Methylcrotonyl-CoA carboxylase
- Propionyl-CoA carboxylase
- Pyruvate carboxylase
The attachment of biotin to various proteins, called biotinylation, is an important process in DNA transcription and replication.
Biotin binds very tightly to the tetrameric protein streptavidin, with a dissociation constant Kd in the order of 10-14M. This is often used in different biotechological applications. Until 2005, very harsh conditions were required to break the biotin-streptavidin bond (Holmberg et al, 2005).
References
- The biotin-streptavidin (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15690449)interaction can be reversibly broken using water at elevated temperatures, Holmberg, A. et al Electrophoresis 2005, 26(3), 501-10.
See also
External links
- Oregon State University (http://lpi.oregonstate.edu/infocenter/vitamins/biotin/)de:Biotin
fr:Biotine it:Biotina lb:Biotin lt:Biotinas nl:Biotine ja:ビオチン pl:Biotyna fi:Biotiini