Biotin

The discovery, isolation and synthesis of biotin started in 1927 with an experiment where rats developed an unusual dermatitis after they were fed only with the protein of hen egg white [14]. The dermatitis could be cured by a substance that was called vitamin H and that is present in many foodstuff. But it took many years, until GYÖRGY et al. [60] identified in 1940 that biotin and vitamin H are identical.

Biotin ( $\rm {C_{10}H_{16}N_2O_3S}$) is a coenzyme that plays a vital role in nearly all organisms (from bacteria to animals) [35]. Like many coenzyms, biotin cannot be synthesised by animals and must be obtained from plants. It is not indispensable for life, but humans and animals with a biotin deficiency can get dermatitis^1.1 or alopecia^1.2. Biotin is a component of many enzymes in the human body and plays a vital role in the degradation of specific proteins (e.g. serum albumin) [13].

Figure 1.1: Biotin

[Chemical structure of biotin, based on [26]]             [Three-dimensional structure of biotin [33]]

Figure 1.1 presents the chemical structure (a) and a three-dimensional image of biotin (b). Biotin consists of an imidazole ring with an attached valerat side chain. The carboxyl group at the end of the chain can bind covalently to the amino-groups of enzymes [127]. The molecular weight of biotin is only 144Da ^1.3 [9] and it is only about 7Å long (see [32] for more information about the structure of biotin and its vitamers).