RECYCLING DEFECTS OF COVALENTLY-BOUND VITAMINS

维生素敏感性糖尿病的生化和遗传研究 酶病导致了一组 可成功治疗的遗传性代谢紊乱， 给予新的洞察力的营养作用的各种 维生素 我们最近证明了一种这样的疾病， 迟发性生物素反应性多发性羧化酶缺乏症， 由生物素酶活性缺乏引起。 这种酶 催化共价结合的生物素从所述膜上除去， 各种辅酶依赖性羧化酶，从而再生 维生素再利用。 为了充分了解基因和 共价结合维生素的营养意义， 现在很清楚它们的新陈代谢和它们的作用方式 必须重新考虑。 正常人生物素酶，纯化至 同质性，将通过生物化学和 免疫学方法。 各种生化方面， 正常生物素酶、其其他生物学功能和亚细胞 定位将进行研究，以更好地阐明酶的作用 在生物素代谢和潜在的遗传缺陷的网站， 其他生物素反应性疾病。 我们将描述 生物素酶缺乏症的生物化学和分子基础 各种免疫学和分子生物学方法。 这些 结果可以解释在本研究中观察到的临床异质性。 并允许更准确地确定 生物素酶缺乏的杂合子。 最后我们将 对脂酰胺酶进行生物化学研究， 释放出另一种共价结合的维生素，硫辛酸。 因为 丙酮酸脱氢酶是一种硫辛酸依赖性酶， 已知这种酶的缺乏会导致乳酸酸中毒， 脂酰胺酶中的主要缺陷可能导致一些 无法解释的乳酸代谢紊乱 拟议 研究将提供一个更全面的了解 酶的代谢作用，回收维生素和它们的 对正常营养的贡献和各种已知的 潜在的维生素缺乏症。

Biochemical and genetic studies of vitamin-responsive enzymopathies have resulted in the elucidation of a group of successfully treatable inherited metabolic disorders and have given new insight into the nutritional role of the various vitamins. We have recently demonstrated that one such disease, late-onset biotin-responsive multiple carboxylase deficiency, is caused by a deficiency of biotinidase activity. This enzyme catalyzes the removal of covalently bound biotin from the various coenzyme-dependent carboxylases, thus regenerating the vitamin for reutilization. To fully understand the genetic and nutritional significance of the covalently bound vitamins it is now clear that their metabolism as well as their mode of action must be reconsidered. Normal human biotinidase, purified to homogeneity, will be characterized by biochemical and immunological methodologies. Various biochemical aspects of normal biotinidase, its other biological functions and subcellular localization will be studied to better elucidate the enzyme's role in biotin metabolism and potential sites for genetic defects in other biotin-responsive disorders. We will characterize the biochemical and molecular basis of biotinidase deficiency using various immunological and molecular biological methods. These results may explain the clinical heterogeneity observed in this disorder and allow more accurate determination of heterozygotes for biotinidase deficiency. Finally, we will conduct biochemical studies of the enzyme, lipoamidase, which releases another covalently bound vitamin, lipoic acid. Because pyruvate dehydrogenase is a lipoic acid-dependent enzyme and deficiency of this enzyme is known to result in lactic acidosis, a primary defect in lipoamidase may be responsible for some unexplained disorders of lactic acid metabolism. The proposed research will provide a more complete understanding of the metabolic role of enzymes that recycle vitamins and their contribution to normal nutrition and a variety of known and potential vitamin deficiency states.