The Mechanism of Biotin Biosynthesis

描述：(申请人提供)生物素(维生素H)参与 细胞代谢作为羧基酶、脱羧酶、 和转羧酶。生物素生物合成的最后一步涉及 将硫插入到二硫代碘中，这是一种具有化学挑战性的反应， 需要在失活的饱和碳原子上形成C-S键。这 转化依赖于Biob基因产物生物素合成酶。生物素 合酶是一种铁-硫(铁-S)蛋白，属于铁硫蛋白家族 S-腺苷蛋氨酸依赖的自由基生成铁-S酶。的新角色 铁-S团簇开始在自由基的生成中涌现 生物素最后一步中的中间体和硫的贡献 综合。虽然铁-S星系团的确切作用还没有完全被理解， 在生物素生物合成中使用铁团簇作为硫供体意味着 新颖的S基铁-S团簇化学。类似的硫基化学可能是 参与S-腺苷蛋氨酸的裂解生成 5？-脱氧腺苷自由基。这项研究提案的主要目标是 将分子生物学和生化方法与 生物物理光谱技术(EPR、吸收/CD/MCD、 共振拉曼光谱、穆斯堡尔谱学和质谱学) 确定Fe-S团簇介导的还原切割的机理 S-腺苷蛋氨酸，发生在 用于生物素生物合成的硫原子的捐赠，以及 生物素的催化生物合成。

DESCRIPTION: (provided by applicant) Biotin (vitamin H) participates in cellular metabolism as the prosthetic group of carboxylases, decarboxylases, and transcarboxylases. The final step of biotin biosynthesis involves the insertion of sulfur into dithiobiotin, a chemically challenging reaction that entails the formation C-S bonds at inactivated, saturated carbon atoms. This transformation is dependent upon the bioB gene product, biotin synthase. Biotin synthase is an iron-sulfur (Fe-S) protein and belongs to the family of S-adenosylmethionine-dependent radical-generating Fe-S enzymes. New roles for Fe-S clusters are beginning to emerge in the generation of radical intermediates and in the donation of sulfur in the final step of biotin synthesis. Although the exact role of the Fe-S cluster is not fully understood, the use of the Fe-cluster as a sulfur donor in biotin biosynthesis implies novel S-based Fe-S cluster chemistry. Similar sulfur-based chemistry could be involved in the cleavage of S-adenosylmethionine to generate the 5?-deoxyadenosyl radical. The major objectives of this research proposal are to use molecular biology and biochemical methodologies together with the application of biophysical spectroscopic techniques (EPR, absorption/Cd/MCD, resonance Raman, and Mossbauer spectroscopies and mass spectrometry) to determine the mechanism of Fe-S cluster-mediated reductive cleavage of S-adenosylmethionine, the nature of the cluster transformation that occurs upon donation of the sulfur atom for biotin biosynthesis, and the requirements for catalytic biosynthesis of biotin.