Phoslactomycins: Biosynthesis & Activity

描述（由申请人提供）：许多细菌天然产物含有取代的？-不饱和-？-内酯。取代基的化学性质大大改变了生物活性。对于天然产物，如福斯曲菌素和磷乳霉素（PLM），取代基是线性聚酮链，其不寻常之处在于它具有多个顺式双键和磷酸基团。PLMs对包括烟曲霉在内的人类真菌病原体表现出显著的选择性和有效的活性。已对编码PLM和fostriecin生物合成过程的DNA进行了克隆、测序和分析。已经表明，这两种天然产物都是由模块化聚酮酶（PKS）产生的。在PLM的情况下，许多生物合成过程已经被破译。通过正在进行的PLM生物合成研究提供的知识和遗传工具允许产生阻断的突变体，混合途径和突变合成方法，以获得基于PLM骨架的新天然产物。这些化合物通常以优异的发酵产率（10-50 mg/L）从发酵中获得，并且在内酯核心周围和δ取代基中包括显著的结构多样性。通过化学和有效的酶促修饰这些新的PLM核心结构，已经获得了额外的结构变化。该提案有四个目标。目标1将测试一个假设，即两个系统中的模块如何在？取代基目的2-3将检验不饱和内酯的顺式双键不是由PKS模块内的典型脱水结构域建立的，而是由丙二酰化途径中间体的前所未有的脱羧消除建立的假设。一系列的化学，生物化学，遗传和结构的方法将调查酶催化的消除反应，确定丙二酰化的中间体是如何产生的，以及这些步骤在PLM生物合成途径的顺序。目标4将集中于评价新的PLM的抗真菌活性，以及它们选择性抗真菌活性的基础。 公共卫生相关性：细菌产生一个小家族的化学相关的天然产物，如fostriecin和phoslactomycin，具有抗癌和抗真菌活性。该项目将结合联合收割机现代技术，如基因工程，有机和酶催化合成，以1）了解这些天然产物是如何制造的，2）产生新的结构相关的化合物，用于人类健康问题的潜在应用。

DESCRIPTION (provided by applicant): A number of bacterial natural products contain substituted ???-unsaturated-?-lactones. The chemical nature of the substituents alters the biological activity considerably. For natural products such as fostriecin and phoslactomycins (PLMs), the ?-substituent is a linear polyketide chain and unusual in that it has multiple cis double bonds and a phosphate group. The PLMs exhibit remarkably selectivity and potent activity against human fungal pathogens, including Aspergillus fumigatus. The DNA encoding the PLM and fostriecin biosynthetic processes have been cloned, sequenced and analyzed. It has been shown that both natural products are generated by modular polyketide synthases (PKSs). In the case of PLM much of the biosynthetic process has been deciphered. The knowledge and genetic tools provided through ongoing PLM biosynthetic studies has allowed the generation of blocked mutants, hybrid pathways, and mutasynthetic approaches to access new natural products based around the PLM skeleton. These compounds are generally obtained in excellent fermentation yield (10-50 mg/L) from fermentations and include significant structural diversity both around the lactone core and in the delta substituent. Additional structural variation has been obtained by chemical and efficient enzymatic modification of these new PLM core structures. The proposal has 4 aims. Aim 1 will test a hypothesis for how modules in both systems establish the unusual cis double bonds in the ?-substituent. Aim 2-3 will test a hypothesis that the cis double bond of the unsaturated lactone, is not established by a canonical dehydration domain within a PKS module, but rather an unprecedented decarboxylative elimination from a malonylated pathway intermediate. A series of chemical, biochemical, genetic and structural approaches will investigate the enzyme-catalyzed elimination reaction, determine how the malonylated intermediate is generated, and the sequence of these steps in the PLM biosynthetic pathway. Aims 4 will focus on evaluating the antifungal activity of new PLMs, and the basis for their selective antifungal activity. PUBLIC HEALTH RELEVANCE: Bacteria produce a small family of chemically related natural products such as fostriecin and phoslactomycin with established anticancer and antifungal activity. This project will combine modern techniques such as genetic engineering, organic and enzyme-catalyzed synthesis to 1) understand how these natural products are made, and 2) generate new structurally-related compounds for potential application in human-health issues.