FIRST STEP OF HEME BIOSYNTHESIS IN MAMMALS

哺乳动物血红素生物合成的第一步

• 批准号: 2017599
• 负责人: GLORIA C. FERREIRA
• 金额: $ 14.53万
• 依托单位: UNIVERSITY OF SOUTH FLORIDA
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-01-01 至 2000-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2017599
• 关键词: 5 aminolevulinate synthase; allosteric site; cofactor; enzyme mechanism; enzyme structure; erythrocytes; genetic transcription; heme; human genetic material tag; isozymes; point mutation; porphyrin biosynthesis; protein structure function; sideroblastic anemia

The long term objective is to understand the role of 5- aminolevulinate synthase (ALAS), both at the enzyme and gene levels, in the regulation of heme biosynthesis in differentiating erythrocytes. ALAS catalyzes the first and rate limiting step in heme biosynthesis, the PLP-dependent reaction of glycine and succinyl-CoA to yield aminolevulinic acid, CoA and CO2. ALAS synthesis, although ubiquitous, occurs predominately in erythrocytes and hepatocytes, where demands are greater because of the synthesis of hemoglobin and cytochrome P-450, respectively. The erythroid-specific isoform of ALAS (ALAS-E) is expressed concomitantly with the differentiation and maturation of the erythroid cells. Recently a heterozygous group of point mutations in the catalytic domain of the ALAS-E enzyme has been found to cause the human genetic disorder X-linked sideroblastic anemia (XLSA). Characterization of the molecular mechanisms of the ALAS- catalyzed reaction and of the regulation of the expression of the ALAS-E gene are essential to design improved therapies for XLSA patients and/or for improved diagnosis for at-risk family members. Studies projected for the next four years will utilize chemical, biochemical, physical and molecular biological approaches to address three major specific aims: i) to define the role of K313 in the mammalian erythroid ALAS-catalyzed reaction; ii) to identify the functionally important residues of the glycine loop in the PLP cofactor binding site of ALAS; and iii) to evaluate transcriptional regulation of the mammalian erythroid ALAS (ALAS) gene. Results from these studies will provide the first characterization of the function and mechanism of ALAS at the molecular level and will elucidate the regulatory mechanism(s) of expression of the ALAS-E in differentiation erythrocytes. Significantly, they will provide the framework for the interpretation of the already identified ALAS-E genetic mutations associated with XLSA.

长期目标是了解 5- 氨基乙酰丙酸合酶 (ALAS)，酶和基因 水平，在分化过程中血红素生物合成的调节 红细胞。 ALAS 催化第一个限速步骤 血红素生物合成，甘氨酸和 PLP 依赖性反应 琥珀酰辅酶A产生氨基乙酰丙酸、辅酶A和CO2。 唉 合成虽然普遍存在，但主要发生在 红细胞和肝细胞，由于以下原因，需求更大 分别合成血红蛋白和细胞色素 P-450。 表达 ALAS 的红系特异性亚型 (ALAS-E) 随着事物的分化和成熟 红细胞。 最近出现了一组杂合的点突变 已发现 ALAS-E 酶的催化结构域 导致人类遗传性疾病X连锁铁粒幼细胞贫血 （XLSA）。 ALAS-分子机制的表征 催化反应及其表达调控 ALAS-E 基因对于设计改进的 XLSA 疗法至关重要 患者和/或改善高危家庭成员的诊断。 预计未来四年的研究将利用化学、 生物化学、物理和分子生物学方法 解决三个主要具体目标： i) 定义 K313 在 哺乳动物红系 ALAS 催化反应； ii) 识别 PLP 中甘氨酸环的功能上重要的残基 ALAS 的辅因子结合位点； iii) 评估转录 哺乳动物红系 ALAS (ALAS) 基因的调控。 这些研究的结果将提供第一个特征 ALAS在分子水平上的功能和机制 将阐明表达的调控机制 分化红细胞中的 ALAS-E。 值得注意的是，他们将 为解释已经存在的问题提供框架 确定了与 XLSA 相关的 ALAS-E 基因突变。