AT-less Type I Polyketide Synthases

描述（由申请人提供）：在美国，癌症导致每4例死亡中就有1例。因此，开发全新的、临床上有用的抗癌药物是国家卫生和研究的当务之急。来那霉素（LNM）、异偏头痛抑制素（iso-MGS）、偏头痛抑制素（MGS）和乳酰亚胺霉素（LTM）是具有前所未有的作用模式的有前途的抗癌药物先导物。一个巨大的挑战是开发制备这些复杂的天然产物及其结构类似物的方法，用于机理研究和临床开发。我们在此竞争性更新申请中建议（i）继续研究LNM、iso-MGS和LTM生物合成，以发现新的化学和酶学，以及（ii）将组合生物合成方法应用于LNM、iso-MGS和LTM生物合成机制，以生产新型抗癌药物。我们的假设是：（i）LNM、iso-MGS和LTM无AT的I型PKS代表了一种新的PKS结构，对它的研究将揭示对PKS催化的分子机制的新见解;（ii）无AT的I型PKS为PKS工程、通过组合生物合成扩大聚酮结构多样性的方法和策略提供了新的机会;（iii）LNM、iso-MGS、和LTM的生物合成是前所未有的，其表征将揭示新的化学和酶学，和（iv）LNM，iso-MGS，MGS和LTM是具有新的作用模式的优秀的抗癌先导物，并且这些天然产物及其结构类似物可以现实地开发成新的抗癌药物。本授权期的具体目标是：（i）LNM、iso-MGS和LTM无AT I型PKS的机制和结构表征，作为研究无AT I型PKS如何与其同源酰基转移酶（AT）相互作用以构成用于聚酮生物合成的功能性PKS大合成酶的模型;（ii）LNM、iso-MGS和LTM生物合成的新型酶的机制和结构表征;和（iii）合理工程化LNM、iso-MGS和LTM途径，用于代谢物过量生产和新的类似物。这些研究的结果包括发现和开发新型抗癌药物先导物和潜在的临床有用的抗癌药物。我们研究的长期目标是在分子水平上了解微生物如何合成复杂的天然产物，并开发和应用组合生物合成方法对天然产物进行抗癌药物的发现和开发。

DESCRIPTION (provided by applicant): Cancer causes 1 of every 4 deaths in the US. The development of fundamentally new, clinically useful anticancer drugs therefore constitutes a national health and research imperative. Leinamycin (LNM), iso-migrastatin (iso-MGS), migrastatin (MGS), and lactimidomycin (LTM) are promising anticancer drug leads with unprecedented modes of action. A great challenge is to develop ways to prepare these complex natural products and their structural analogs for mechanistic studies and clinical development. We propose in this Competitive Renewal application (i) to continue to study LNM, iso-MGS, and LTM biosynthesis to discover novel chemistry and enzymology and (ii) to apply combinatorial biosynthesis methods to the LNM, iso-MGS, and LTM biosynthetic machinery for production of novel anticancer drugs. Our hypotheses are (i) the LNM, iso-MGS, and LTM AT-less type I PKSs represent a novel PKS architecture, the studies of which will reveal new insights into the molecular mechanism of PKS catalysis, (ii) AT-less type I PKSs provide new opportunities for PKS engineering, methods and strategies for expanding polyketide structural diversity by combinatorial biosynthesis, (iii) several other aspects in LNM, iso-MGS, and LTM biosynthesis are unprecedented, the characterization of which will uncover new chemistry and enzymology, and (iv) LNM, iso-MGS, MGS, and LTM are excellent anticancer leads with novel modes of action, and these natural products and their structural analogs could be realistically developed into new anticancer drugs. The specific aims for this grant period are: (i) mechanistic and structural characterization of the LNM, iso-MGS, and LTM AT-less type I PKSs as models to investigate how AT-less type I PKS interacts with its cognate acyltransferase (AT) to constitute a functional PKS megasynthase for polyketide biosynthesis; (ii) mechanistic and structural characterization of novel enzymes for LNM, iso-MGS, and LTM biosynthesis; and (iii) rational engineering of the LNM, iso-MGS, and LTM pathways for metabolite overproduction and novel analogs. The outcomes of these studies include the discovery and development of novel anticancer drug leads and potentially clinically useful anticancer drugs. The long-term goal of our research is to understand at a molecular level how microorganisms synthesize complex natural products and to develop and apply combinatorial biosynthesis methods to natural products for anticancer drug discovery and development.