Function and Effects of Biotin

Bhullar RP and Dakshinamurti K. The effects of biotin on cellular functions in HeLa cells. J. Cell Physiol. 122 425-430 (1985). 

A bound divalent metal ion, usually Mn2+, is required in the transcarboxylation step. A possible function is to assist in enolization of the carboxyl acceptor. However, measurement of the effect of the bound Mn2+ on 13C relaxation times in the substrate for pyruvate carboxylase indicated a distance of 0.7 ran between the carbonyl carbon and the Mn2+, too great for direct coordination of the metal to the carbonyl oxygen.68 Another possibility is that the metal binds to the carbonyl of biotin as indicated in Eq. 14-11. Pyruvate carboxylase utilizes two divalent metal ions and at least one monovalent cation.683... 

Vitamin Biotin RDA/AI Men women 30 MQ/d Physiological Function Coenzyme in the synthesis of fat, glycogen, and amino acids Adverse Effects of Excessive Consumption No adverse effects have been reported ... 

Al), present in macrophages, responsible for cardiovascular disorders. Microscopy studies revealed a very good colocalization of receptors and ligands, while no such effect was observed with control cells, which did not possess the Al receptor. Further loading of the above described biotin-avidin functionalized vesicles with fluorescent labels (calcein) allowed a microscopic observation of the binding and uptake of the vesicles by the cells [175], Again, the vesicles preferred to attach to macrophages and they were observed to actually enter the cells by endocytosis. After some time, calcein was released which could be observed by fluorescence microscopy. 

As Lonza had complete freedom to modify its own process for (d)-(+)-biotin, and selective introduction of substituents at N-l (through choice of starting material) and N-3 (through functionalization of 2) was simple, the effect of substituents on the hydrogenation was briefly studied. The results for a selection of the N-l- and N-3-substituted analogues investigated in Fig. 6 are summarized in Tab. 2 and Tab. 3, respectively. 

Biotin is central to the metabolism of carbohydrates, amino acids, and lipids as biotin is the prosthetic group of the carboxylases. In addition to this metabolic function, biotin influences transcription in organisms ranging from bacteria to humans. Biotin exerts complex effects on cell cycle and gene transcription through epigenetic mechanisms. Nuclear biotin holocarboxylase synthetase seems to interact with other chromatin proteins to form a multiprotein gene repressor complex. 

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