Type III Polyketide Synthases: Structure and Mechanism

III 型聚酮化合物合成酶：结构和机制

• 批准号: 6742498
• 负责人: BRADLEY S MOORE
• 金额: $ 34.49万
• 依托单位: UNIVERSITY OF ARIZONA
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-06-15 至 2007-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6742498
• 关键词: Escherichia coli; Mycobacterium tuberculosis; Pseudomonas; Streptomyces; X ray crystallography; active sites; acyl carrier protein; antibiotics; antineoplastic antibiotics; bacterial proteins; biological products; enzyme mechanism; enzyme structure; enzyme substrate complex; fatty acid biosynthesis; gene mutation; genetic library; microorganism metabolism; polyketide synthase; protein engineering; protein structure function; sesquiterpenes; vancomycin

A new mechanism of polyketide assembly has emerged in bacteria for the biosynthesis of small aromatic residues that serve as important structural elements in a growing number of biologically active natural products. These small aromatic polyketides are synthesized by homodimeric (type III) polyketide synthases (PKSs) that are phylogenetically and biochemically related to ubiquitous plant PKSs such as chalcone synthase. Thus far, type III PKSs have been shown to be responsible for the biosynthesis of natural products such as 1,3,6,8- tetrahydroxynaphthalene (THN) and the formation of key components of more complex antimicrobial and antitumor natural products such as vancomycin, naphterpin, marinone, and kendomycin. While type III PKSs are architecturally simple, they arguably represent the most sophisticated PKSs mechanistically since embodied within their homodimeric architecture is the catalytic machinery necessary for starter molecule recognition and loading, malonyl- CoA decarboxylation and polyketide chain extension, and ultimately, multiple pathways for termination. Their simple gene and protein architecture makes them amendable for study using a variety of sophisticated approaches including heterologous biosynthesis, in vitro and in vivo biochemical analysis, directed and random approaches towards enzyme engineering, and atomic resolution protein x-ray crystallography. Although the analysis of related plant enzymes is fairly mature, research on the bacterial counterparts is only beginning and can be expected to yield novel, interesting, and potentially important information on these simple condensing enzymes. Moreover, the mechanistic and structural understanding of bacterial type III PKSs is likely to be relevant for the productive reengineering of modular type I and iterative type II bacterial PKSs. With the high resolution three-dimensional crystal structure of the first bacterial PKS, THN synthase from Streptomyces coelicolor A3(2), nearly in hand, the stage is set for a comprehensive structural and mechanistic analysis of this new subclass of bacterial PKS. Studies will extend to other bacterial type III PKSs, including those involved in the biosynthesis of the clinically important glycopeptide vancomycin, the broad spectrum antibiotic 2,4- diacetylphloroglucinol, and the antitumor antibiotic marinone.

在细菌中出现了一种新的聚酮化合物组装机制，用于小型芳族残基的生物合成，这些残留物是越来越多的生物活性天然产物中重要的结构元素。 这些小的芳族聚酮化合物由同二聚体（III型）聚酮化合物合酶（PKSS）合成，它们在系统发育和生化上与无处不在的植物PKS（如Chalcone合酶）相关。 到目前为止，III型PKS已被证明是造成天然产物的生物合成，例如1,3,6,8-四氢羟基苯二酚（THN）以及更复杂的抗菌和抗肿瘤和抗肿瘤天然产物的关键组成部分的形成，例如，宽癌蛋白，含量雄性霉素，Marinyone和Kendomycin。 虽然III型PKS在建筑上很简单，但可以说是机械机理的最复杂的PKS，因为在其同型二聚体结构中体现的是起动分子识别和载荷，Malonyl-COA脱羧和聚酮化合物链的催化机制，以及最终的终止途径。 它们的简单基因和蛋白质结构使它们可以使用各种复杂的方法进行研究，包括异源生物合成，体外和体内生物化学分析，酶工程和原子分辨率分辨率蛋白质X射线晶体学的定向和随机方法。 尽管对相关植物酶的分析相当成熟，但对细菌对应物的研究才刚刚开始，可以预期就这些简单的凝结酶产生新颖，有趣且潜在的重要信息。 此外，细菌III型PKS的机械和结构理解可能与模块化I型和II型II型细菌PKS的生产性重新设计有关。 使用第一个细菌PK的高分辨率三维晶体结构，来自链霉菌链球菌A3（2）的合成酶几乎掌握在手中，该阶段设定为对这一新型细菌PKS的全面结构和机械分析。 研究将扩展到其他细菌III型PKS，包括参与临床上重要糖肽万古霉素的生物合成的细菌，宽光谱抗生素2,4-二酰二乙酰氯酸葡萄糖醇和抗肿瘤抗生素抗生素海洋酮。