Biotin

Abstract

Biotin is a vitamin that is a cofactor for enzymes involved in carbon dioxide metabolism. Biotin‐dependent enzymes catalyse carboxylations, decarboxylations and transcarboxylations. These reactions are involved in a variety of metabolic functions from fatty acid synthesis to gluconeogenesis and are found in all animals, plants and bacteria. The common feature of biotin‐dependent enzymes is they are multifunctional. They contain two separate active sites that catalyse distinct chemical reactions. The biotin moiety, which is covalently attached to the enzyme via the amino acid lysine, alternates between the two distinct active sites. In one active site, biotin is carboxylated, whereas, in the other active site, the carboxyl group is transferred to an acceptor molecule. Avidin and streptavidin are proteins that bind biotin very tightly. The high affinity between biotin and avidin/streptavidin is utilised for a variety of biotechnological techniques such as protein purification and immunoassays such as Western blotting. Key Concepts Biotin is a vitamin. Biotin is a cofactor for enzymes involved in CO 2 metabolism. Biotin‐dependent enzymes catalyse carboxylation, decarboxylation and transcarboxylation reactions. Biotin‐dependent enzymes are multifunctional and contain two distinct active sites. Biotin, which is covalently attached to a protein, moves between each of the two active sites. The two active sites and the biotin carrier protein can comprise three separate proteins that form a complex or they can form domains on a single polypeptide. The biotin‐dependent enzyme acetyl‐CoA carboxylase is an emerging target for antibiotic development. The proteins avidin and streptavidin bind biotin very tightly and with a high degree of specificity. The very high affinity and specificity of the biotin avidin/streptavidin interaction is used for many biotechnology techniques.