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Biotin

Biotin (vitamin H or vitamin B7) is a vitamin which is important for humans and animals and whose deficiency may cause, for example, seborrhoea, dermatitis, loss of appetite and lassitude. Accordingly, biotin is a beneficial additive to human and animal foods. Biotin is related to fatty acid synthesis or saccharide metabolism as a coenzyme of a carboxylase. Coenzymes are a group of small organic molecules with distinct chemical functionalities, which are usually unavailable or insufficient in the side chains of the 20 naturally occurring amino acids. A number of metabolic protein enzymes require coenzymes to act as accessory molecules to provide necessary reactivities. Three common coenzymes, coenzyme A (CoA), nicotinamide adenine dinucleotide (NAD), and flavin adenine dinucleotide (FAD) carry out a variety of acyl group transfer and electron/hydride transfer reactions in metabolism. Biotin (vitamin H) plays an essential role as coenzyme in enzyme-catalyzed carboxylation and decarboxylation reactions. Biotin is thus an essential factor in living cells. Biotin is an indispensable element in intermediary metabolism in many organisms since it is an essential factor of biotin-dependent carboxylases important in fatty acid synthesis, gluconeogenesis, and amino acid metabolism. Biotin is a basic component of cell metabolism that acts as a cofactor that binds covalently to carboxylases to facilitate the transfer of carboxyl groups during enzymatic carboxylation, decarboxylation and transcarboxylation reactions. Almost all animals and some microorganisms have to take biotin in from the outside because they are unable to synthesize biotin themselves. It is thus an essential vitamin for these organisms. Bacteria, yeasts and plants by contrast are themselves able to synthesize biotin from precursors. Biotin induces the up regulation of the enzyme glucokinase (GK) in the pancreas and enhances the process of glucose-induced insulin secretion. In addition, biotin counteracts the effect HCA has on the pancreas. HCA tends to inhibit glucose-induced insulin secretion, while biotin facilitates it by activating GK. Together, HCA and biotin maximize pancreatic fuel homeostasis. Biotin is necessary for the metabolism of carbohydrates, proteins, and fats and is needed for healthy skin and hair. Vitamin H also proved to be particularly effective in the treatment of the seborrheal dermatitis in the newborn. Biotin deficiency may result in dermatological disorders.

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