Biotin, also known as Vitamin B7 or Vitamin H, is a water-soluble vitamin with an important role in various biological processes within living organisms. “Biotin Sigma” refers to Sigma-Aldrich, a prominent global supplier of chemical compounds for scientific research, highlighting biotin’s widespread use as a reliable laboratory tool.
Biotin’s Essential Role in Biology
Biotin serves as a cofactor for specific carboxylase enzymes, which are proteins that facilitate chemical reactions involving the addition of a carboxyl group. These biotin-dependent carboxylases are involved in key metabolic processes, including the metabolism of fatty acids, amino acids, and carbohydrates. For instance, acetyl-CoA carboxylase, a biotin-dependent enzyme, converts acetyl-CoA to malonyl-CoA, a building block for fatty acid synthesis.
Another example is pyruvate carboxylase, which participates in gluconeogenesis, forming glucose from non-carbohydrate sources. Propionyl-CoA carboxylase and 3-methylcrotonyl-CoA carboxylase are also biotin-dependent enzymes involved in the breakdown of certain amino acids. Mammals obtain biotin from their diet, primarily from plants and microbes.
Beyond its role in metabolism, biotin also participates in other cellular processes. It is involved in epigenetic gene regulation, which refers to changes in gene activity that do not involve alterations to the underlying DNA sequence. Biotin can covalently attach to specific lysine residues in histone proteins that package DNA into chromatin. This modification, called histone biotinylation, influences chromatin structure and gene expression.
Biotinylation of histone H4, for example, is associated with gene silencing and the cellular response to DNA damage. This suggests biotin influences gene expression and DNA repair. Biotin also plays a role in cell signaling, with biotin-dependent signals mediated by molecules such as biotinyl-AMP and various transcription factors.
Biotin as a Versatile Tool in Research
Scientists use biotin’s strong and specific binding affinity for the proteins avidin and streptavidin. This interaction, known as the biotin-(strept)avidin system, is one of the strongest non-covalent interactions in nature (Kd ~10-14 to 10-15 mol/L), making it resistant to many denaturing agents and extreme conditions. This robust binding makes biotin an invaluable tool for various research applications, often supplied by companies like Sigma-Aldrich.
Biotin is commonly used in detection systems, such as immunoassays like Enzyme-Linked Immunosorbent Assay (ELISA) and Western blotting. In these techniques, biotin is attached to antibodies or other molecules. Streptavidin conjugated to an enzyme or fluorescent tag then detects the biotinylated molecule, amplifying the signal for improved sensitivity, especially for low-abundance targets. In immunohistochemistry, where specific molecules are detected in tissue samples, researchers often block endogenous biotin to avoid inaccurate background signals.
Biotin is also used for purification and isolation, particularly in affinity chromatography. Researchers attach biotin to a protein, nucleic acid, or specific cell type. The biotinylated molecule is passed over a column packed with streptavidin-linked beads, which captures the target. This allows selective separation and purification from complex mixtures. Eluting bound molecules often requires harsh conditions due to the strong biotin-streptavidin bond. However, some methods use competitive elution with free biotin or monomeric avidin for milder release.
In cell culture and growth media, biotin supplements support the growth of various cell types, including mammalian cells like oligodendrocytes. For example, biotin can protect oligodendrocyte lineage cells from metabolic injury and enhance myelin-like ensheathment, relevant for neurological research. It is also incorporated into bacterial growth media as an essential nutrient for microbial cultures. Biotin is also used for labeling and tracking molecules in experiments, allowing scientists to monitor their movement or interaction.