Biotin
General
Chemical formula	C10H16N2O3S
Molecular weight	244.31 g/mol
Other names
Vitamin B7 Vitamin H
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
Dry scaly skin Fatigue Loss of appetite Nausea and vomiting Mental depression Tongue inflammation High cholesterol
Excess symptoms
None
Common sources
Liver and kidney Dairy products Some seafood, especially oysters, lobster, and salmon Yeast

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^-.

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 K_d in the order of 10^-14. This is often used in different biotechological applications. Until 2005, very harsh conditions were reqired to break the biotin-streptavidin bond (Holmberg et al, 2005).

References

• The biotin-streptavidininteraction can be reversibly broken using water at elevated temperatures, Holmberg, A. et al Electrophoresis 2005, 26(3), 501-10.

See also

• Biotinylation

External links

• Oregon State University