Discovering New Anti-Infective Agents from Lysobacter

描述（由申请人提供）：多药耐药已成为人类死亡和发病的一个日益重要的原因。发现新的抗感染药物是一项迫切而持续的需要。生物活性天然产物是抗感染药物的主要来源。传统上，土壤细菌，特别是革兰氏阳性链霉菌，一直是生物活性天然产物的主要来源。然而，许多无处不在的土壤和水中的居民，如革兰氏阴性滑翔细菌溶菌，尽管它们是天然产物的多产生产者，但它们在很大程度上仍未被探索。本提案描述了从新来源发现和评估具有新结构和有效活性的新抗感染药物的研究计划。重点是破译它们的生物合成和调节机制。具体而言，将研究两组生物活性天然产物HSAF和WAP-8294A。HSAF （dihydromaltophilin）是一种多环四聚乳酸大内酰胺（PTM），是一类具有新化学性质和新作用方式的新型抗真菌化合物。为了使HSAF成为一种新型的抗真菌药物，了解其化学结构的生物合成机制是十分重要的。HSAF生物合成基因簇仅包含一个单模块聚酮合成酶-非核糖体肽合成酶（PKS/NRPS），其两侧有六个氧化还原酶级联，尽管HSAF生物合成显然需要两个独立的六肽链，它们通过两个酰胺键由一个氨基酸（鸟氨酸）连接在一起。该系统代表了前所未有的迭代PKS/NRPS混合系统。本文的目的是阐明由“氧化还原酶调控的迭代PKS/NRPS”催化的反应，从而导致独特的PTM结构。WAP-8294A是至少20个环状脂沉肽的复合物，对耐甲氧西林金黄色葡萄球菌（MRSA， ED5014比万古霉素（一种“最后手段”抗生素）活性高）具有有效活性。由于产率非常低，只有该复合物的主要成分WAP-8294A2（由aRigen制药公司）处于临床研究中。尽管这些化合物在近15年前首次被分离出来，其中一种化合物正在临床研究中，但它们的生物合成基因直到2011年才被发现。目的是确定WAP生物合成和调控的分子机制，特别是脂肪酸掺入导致结构多样性的机制。了解HSAF和WAP-8294A的生物合成及其调控机制，是对这两类极具生物活性的天然产物进行合理的生物合成工程、提高生产效率和优化结构活性的重要一步。此外，由于溶杆菌是尚未开发的多产的天然产物生产者，本研究将为发现新的抗感染药物开辟新的方向。

DESCRIPTION (provided by applicant): Multi-drug resistance has become an increasingly important cause of mortality and morbidity in humans. It is a pressing and continual need to discover new anti-infective agents. Bioactive natural products are a major source of anti-infective drugs. Traditionally, soil bacteria, especially the Gram-positive Streptomyces, have been the primary source for bioactive natural products. However, many ubiquitous inhabitants of soil and water, such as the Gram-negative gliding bacteria Lysobacter, remain largely unexplored, even though they are prolific producers of natural products. This proposal describes a research plan to discover and evaluate new anti-infectives with novel structures and potent activities from the new sources. The focus is on deciphering their biosynthetic and regulatory mechanisms. Specifically, two groups of bioactive natural products, HSAF and WAP-8294A, will be investigated. HSAF (dihydromaltophilin) is a polycyclic tetramate macrolactam (PTM) and represents a novel type of antifungal compounds with new chemistry and new mode of action. To develop HSAF as a new type of antifungal antibiotics, it is important to understand the biosynthetic mechanism for the novel chemical structure. The HSAF biosynthetic gene cluster contains only a single-module polyketide synthase-nonribosomal peptide synthetase (PKS/NRPS), flanked by a cascade of six redox enzymes, although HSAF biosynthesis apparently requires two separate hexaketide chains that are linked together by one amino acid (ornithine) via two amide bonds. This system represents an unprecedented iterative PKS/NRPS hybrid. The goal here is to illustrate the reactions catalyzed by the "redox enzymes-modulated iterative PKS/NRPS", which lead to the distinct PTM structure. WAP-8294A are a complex of at least 20 cyclic lipodepsipeptides with a potent activity against Methicillin-Resistant Staphylococcus aureus (MRSA, ED5014 times more active than vancomycin, a "last resort" antibiotic). Due to a very low yield, only the major component of the complex, WAP-8294A2, is in clinical studies (by aRigen Pharmaceuticals). Although the compounds were first isolated nearly 15 years ago and one of them is in clinical studies, their biosynthetic genes were just identified in 2011. The goal here is to determine the molecular mechanisms for WAP biosynthesis and regulation, particularly the mechanism for fatty acid incorporation that leads to structural diversity. The understanding of the biosynthetic and regulatory mechanisms for HSAF and WAP-8294A is an essential step toward rational biosynthetic engineering, productivity improvement and structure-activity optimization of these two groups of very promising bioactive natural products. In addition, because Lysobacter are prolific natural product producers that have not been exploited, this research will open a new direction to discovering new anti-infective drugs.