Phoslactomycins: Biosynthesis & Activity

描述(申请人提供)：一些细菌天然产品含有取代的？-不饱和-？-内酯。取代基的化学性质极大地改变了生物活性。对于天然产物，如福斯特里菌素和磷乳霉素(PLM)，？-取代基是线性聚酮链，不同寻常的是它有多个顺式双键和一个磷酸基团。PLM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强大的活性。编码PLM和Fostriecin生物合成过程的DNA已经被克隆、测序和分析。研究表明，这两种天然产物都是由模块化聚酮合成酶(PKSS)产生的。在PLM的案例中，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，使得能够产生受阻的突变体、杂交途径和突变合成方法，以获得基于PLM骨架的新天然产品。这些化合物通常从发酵中获得优良的发酵产率(10-50 mg/L)，并且在内酯核心和三角洲取代基中都具有显著的结构多样性。通过对这些新的PLM核心结构进行化学和高效的酶修饰，获得了额外的结构变化。该提案有4个目标。目标1将检验一个假设，即两个系统中的模块如何在？-取代基中建立不寻常的顺式双键。目的2-3将验证一种假设，即不饱和内酯的顺式双键不是由PKS模块中的典型脱水结构域建立的，而是从丙二酸化途径中间体史无前例的脱羧基消除。一系列的化学、生化、遗传和结构方法将研究酶催化的消除反应，确定丙二酸化中间体是如何产生的，以及这些步骤在PLM生物合成途径中的顺序。AIMS 4将重点评估新的PLM的抗真菌活性，以及它们选择性抗真菌活性的基础。

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.