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-氨基酮戊酸合成酶(ALAS)是α-氧代氨基合酶家族中依赖于吡哆醛5‘-磷酸(PLP)的一种酶，催化哺乳动物血红素生物合成途径的第一步和调控步骤。编码红系ALAS亚型的基因突变会导致X连锁铁粒母细胞贫血(XLSA)，这是一种导致组织铁水平升高的红细胞生成性疾病。基于吡哆醇的治疗XLSA的前景取决于对ALAS机制、辅因子结合口袋(PLP-Fold)及其相互关系的了解。正是活性部位的设计，包括PLP辅因子-蛋白质相互作用，在PLP依赖的酶催化的广泛反应中区分了一种类型的反应。P.I.S实验室最近对ALAS活性中心的结构和机制的研究(1996年至2002年)为检验以下3个假说奠定了基础： 1.PLP辅因子化学的调节控制了ALAS的酶机制。 2.通过对依赖于PLP的羧胺合成酶家族的蛋白质骨架进行微小的修饰，可以获得ALAS的底物特异性，该家族具有相同的PLP结合折叠和催化化学。 3.ALA和谷氨酸L半醛氨基变构酶(GSA-AT)是两种依赖PLP的酶，它们都能产生5-氨基乙酰丙酸(ALA)，并在ALA的两条天然生物合成途径(如动植物中)中发挥关键作用。ALA和谷氨酸半醛氨基变构酶(GSA-AT)的不同催化化学性质可以通过一个初级蛋白质支架的“进化”而产生。 这些研究为建立ALAS和其他α-羟胺合酶之间的结构/功能关系提供了一种新的策略。此外，拟议的研究提供了一种新的方法来理解改组蛋白结构域如何改变功能以及酶活性部位如何进化；这一策略有望成为确定人类基因组中未知基因功能的关键。