5-Aminolevulinate Synthase and Heme Biosynthesis

5-氨基乙酰丙酸合酶和血红素生物合成

• 批准号: 6851726
• 负责人: GLORIA C. FERREIRA
• 金额: $ 20.51万
• 依托单位: UNIVERSITY OF SOUTH FLORIDA
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-02-15 至 2007-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6851726
• 关键词: 5 aminolevulinate synthase; X ray crystallography; active sites; catalyst; chemical kinetics; cofactor; conformation; enzyme activity; enzyme biosynthesis; enzyme mechanism; enzyme substrate; molecular dynamics; myelin proteolipid; porphyrin biosynthesis; protein structure function; spectrometry; transaminases

DESCRIPTION (provided by applicant): 5-Aminolevulinate synthase (ALAS), a pyridoxal 5'-phosphate (PLP)-dependent enzyme of the alpha-oxoaminesynthase family, catalyzes the first and regulatory step of the mammalian heme biosynthetic pathway. Mutations in the gene encoding the erythroid ALAS isoform cause X-linked sideroblastic anemia (XLSA), an erythropoietic disorder resulting in increased tissue iron levels. The prospect of developing pyridoxine-based therapies of universal efficacy for XLSA relies on the knowledge of the mechanism of ALAS, the cofactor-binding pocket (PLP-fold) and their relationship. It is the design of the active site, entailing the PLP cofactor-protein interaction, that discriminates one type of reaction among the wide gamut of PLP-dependent enzyme-catalyzed reactions. Recent studies in the P.I.'s laboratory on the architecture of the active site and mechanism of ALAS (1996-2002)set the stage for the following 3 hypotheses to be tested: 1. Modulation of the PLP cofactor chemistry controls the enzymatic mechanism of ALAS. 2. Substrate specificity of ALAS can be acquired through minor modifications of the protein scaffold for the ctoxoaminesynthase family of PLP-dependent enzymes, which possesses the same general PLP-binding fold and chemistry of catalysis. 3. The distinct catalytic chemistries of ALAS and glutamate l-semialdehyde aminomutase (GSA-AT), two PLP-dependent enzymes which both produce 5-aminolevulinate (ALA) and play crucial roles in the two natural ALA biosynthetic pathways (e.g., in animals and plants), can be generated by "evolution" of a primary protein scaffold. The proposed studies provide a new strategy to establish structure/function relationships within ALAS and other alpha-oxoamine synthase enzymes. Further, the proposed studies provide a novel approach to understanding how shuffling protein structural domains changes function and how enzyme active sites evolve; this strategy promises to be a key particularly for determining the function of unidentified genes in the human genome.

描述（由申请人提供）： 5-氨基乙酰丙酸合酶 (ALAS) 是 α-氧代胺合酶家族的一种 5'-磷酸吡哆醛 (PLP) 依赖性酶，催化哺乳动物血红素生物合成途径的第一步和调节步骤。编码红系 ALAS 亚型的基因突变会导致 X 连锁铁粒幼细胞贫血 (XLSA)，这是一种导致组织铁水平升高的红细胞生成障碍。开发基于吡哆醇的对 XLSA 具有普遍疗效的疗法的前景依赖于对 ALAS 机制、辅因子结合袋（PLP 折叠）及其关系的了解。正是活性位点的设计，需要 PLP 辅因子-蛋白质相互作用，才能在广泛的 PLP 依赖性酶催化反应中区分出一种类型的反应。 P.I. 实验室最近对 ALAS 活性位点结构和机制的研究（1996-2002）为测试以下 3 个假设奠定了基础： 1. PLP 辅因子化学的调节控制 ALAS 的酶促机制。 2. ALAS 的底物特异性可以通过对 PLP 依赖性酶的甲氧胺合酶家族的蛋白质支架进行微小修饰来获得，该家族具有相同的一般 PLP 结合折叠和催化化学。 3. ALAS 和谷氨酸 L-半醛氨基变位酶 (GSA-AT) 的独特催化化学性质，这两种 PLP 依赖性酶均产生 5-氨基乙酰丙酸 (ALA)，并在两种天然 ALA 生物合成途径中发挥关键作用（例如在动物中）和植物），可以通过初级蛋白质支架的“进化”产生。 拟议的研究提供了一种在 ALAS 和其他 α-氧代胺合酶内建立结构/功能关系的新策略。此外，拟议的研究提供了一种新的方法来理解改组蛋白质结构域如何改变功能以及酶活性位点如何进化；这一策略有望成为确定人类基因组中未识别基因功能的关键。