RECYCLING DEFECTS OF COVALENTLY-BOUND VITAMINS

维生素反应性的生化和遗传学研究 酶病导致了一组 可成功治疗遗传性代谢紊乱，并已 对各种营养成分的营养作用有了新的认识 维他命。我们最近证明了一种这样的疾病， 晚发性生物素反应性多发性羧基酶缺乏症 由生物素酶活性不足引起的。这种酶 催化将共价结合的生物素从 各种辅酶依赖的羧基酶，从而再生 可重复利用的维生素。为了充分了解遗传和 共价结合维生素的营养意义 现在很清楚，他们的新陈代谢和他们的行动模式 必须重新考虑。正常人生物素酶，纯化至 同质性，将以生化和 免疫学方法学。不同的生物化学方面 正常生物素酶及其其他生物学功能和亚细胞 将进行定位研究，以更好地阐明该酶的作用 在生物素代谢和遗传缺陷的潜在位置 其他生物素反应性疾病。我们将描述 生物素酶缺乏症的生化和分子基础研究 各种免疫学和分子生物学方法。这些 结果可能解释临床异质性在此观察到。 无序，并允许更准确地确定 生物素酶缺乏症杂合子。最后，我们会 对脂酰胺酶进行生化研究，该酶是 释放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的酶， 这种酶的缺乏已知会导致乳酸酸中毒， 脂酰胺酶的原发缺陷可能是部分原因 原因不明的乳酸代谢紊乱。建议数 研究将使我们更全面地了解 回收维生素的酶及其代谢作用 对正常营养的贡献和各种已知和 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.