CoFactor: Biotin

General information

2D representation

Key facts

Tags

• sulfur-containing cofactors

Molecular function

Biotin's main function as a cofactor is to transfer CO₂ from one active site of an enzyme complex to another. It can also transfer C₂-units [1].

Biotin further regulates gene expression, for instance by biotinylation of histones [1].

Chemical properties

In all cases, biotin is covalently bound to its partner enzyme and serves as a CO₂-carrier between bicarbonate and the acceptor substrate [1].

Pathways

The cofactor is essential for fatty acid biosynthesis [1].

Comment

The biotin requirement is very low, so the only nutritional deficiency is found in patients with a diet rich in raw egg-white (avidin from raw egg white has a high affinity to biotin). Otherwise there are mainly genetic disorders, resulting from a loss of function of biotinidase (the recycling enzyme) or holocarboxylase sythetase (the biotin inserting enzyme) [1].

Part of the required biotin is produced by the intestinal flora [1]. Biotinidase recycles biotin from enzymes gained from food sources [1]. Organic acideria can result from multi-carboxylase deficiency [1]. Other resulting diseases include neurological disorders and developmental delay [1].

References

[1]	pubmed:17898891
[2]	pubmed:17898894
[3]	pubmed:17898888
[4]	pubmed:17898895