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Biotin

1 Definition

Biotin is a water soluble B vitamin with an energy releasing function.

2 Structure

Biotin consists of an imidazole ring, a thiophene ring and a valeric acid chain (also called pentanoic acid).

3 Biochemistry

Biotin acts as a coenzyme in carboxylation reaction catalyzed by caboxylases. Biotin is bound to an ε-amino group of a lysine residue of the enzyme, forming a biotin-enzyme complex. Carbon dioxid (CO2) first binds to a nitrogen atom of the imidazole ring of biotin resulting in a carboxybiotin-enzyme complex. The carboxylation of the biotin-enzyme complex is an ATP dependent process. Eventually, the carbon dioxid is transferred to the substrate (carboxylation of the substrate). Afterwards, the biotin-enzyme complex is able to catalyze another carboxylation reaction.

4 Requirement

0.1-0.3 mg/day

5 Deficiency

Even though a deficiency of biotin is very rare in human beings, it can occur in people consuming a lot of unboiled egg-white since it contains high amounts of the protein avidin, which usually becomes denatured by cooking. Avidin binds biotin with strong affinity and thereby prevents its absorption in the small intestine.

Symptoms of biotin deficiency:

6 References

Tiberiu Nistor - Basic in descriptive biochemistry

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