Chemical and physical properties of biotin Domina Petric, MD

Essential features of the chemical structure: Conjoined ureido and tetrahydrothiophene nuclei Ureido 3′ nitrogen is sterically hindered, preventing substitution Ureido 1′ nitrogen is poorly nucleophilic November 28, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Biotin nomenclature Biotin is the trivial designation of the compound cis-hexahydro-2-oxo-1H-thieno[3,4-d]imidazole-4-pentanoic acid, also known as vitamin H, vitamin B7 and coenzyme R. November 28, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Chemical and physical properties Biotin is a white crystalline substance that, in dry form, is fairly stable to air, heat and light. In solution, it is sensitive to degradation under strongly acidic or basic conditions. November 28, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Chemical and physical properties Its structure consists of a planar ureido nucleus and a folded tetrahydrothiophene (thiophane) nucleus, which results in a boat configuration with a plane of symmetry passing through the S-1, C-2′, and O positions in such a way as to elevate the sulfur atom above the plane of the four carbons. November 28, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Chemical and physical properties The molecule has three asymmetric centers. Of the eight possible stereoisomers, only the (+)-isomer (called d-biotin) has biological activity. November 28, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Chemical and physical properties Biotin is covalently bound to its enzymes by an amide bond to the ε-amino group of a lysine residue and C-2 of the thiophane nucleus. This bond is flexible, allowing the coenzyme to move between the active centers of some enzymes. November 28, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Chemical and physical properties The biotin molecule is activated by polarization of the O and N-1′ atoms of the ureido nucleus. This leads to increased nucleophilicity at N-1′, which promotes the formation of a covalent bond between the electrophilic carbonyl phosphate formed from bicarbonate and ATP, and allows biotin to serve as a transport agent for CO2. November 28, 2018 Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008.

Literature Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc. 2008. November 28, 2018