Biosynthesis of polyketide antibiotic mupirocin by Pseudomonas fluorescens

生物系统为许多不同的目的构建复杂的分子--构建细胞和超细胞结构的积木，驱动活细胞的催化和能量存储系统，允许生物内部和生物之间通信和信息存储的信使分子，最后是允许防御或攻击其他生物的分子。人类已经学会了开发这些天然化合物中的许多，尤其是那些充当抗生素的化合物。有一类化合物是非常重要的，聚酮类化合物是非常重要的，因为它们包括许多具有非常多样化的结构的分子，这些分子涵盖了一系列有用的活性-不仅是抗菌药物，而且还有抗真菌、抗癌和抗胆固醇药物，仅举几例。通常，这些化合物的分子“骨架”是通过在装配线上连接简单的构建块来制造的，每个构建块由一个单独的“模块”添加，该模块还对新片段进行一系列(通常是三个)修饰之一(称为I型PKS途径)。得到的分子链可以有不同的长度和不同的修饰组合，然后可以用不同的侧链来装饰，以产生独特的产品(裁剪)。然而，越来越多的非典型途径正在被发现，这些途径似乎使用了尚未定义的额外机制。这些方法提供了以受控方式生产新结构的方法。在荧光假单胞菌中发现的一种这样的途径，合成了临床上重要的抗生素莫匹罗星。它对革兰氏阳性菌最有效，尤其用于对抗最危险的超级细菌之一的耐甲氧西林金黄色葡萄球菌(MRSA)。莫匹罗星的生物合成涉及一个非典型的I型PKS以及大量的“剪裁”酶，我们发现其中一些酶与PKS一起作用于构建莫匹罗星的主干。这与典型的第一类公钥基础设施模块形成对比，后者本身包含建立主干所需的所有信息。该项目将微生物分子遗传学、生物化学和化学相结合，研究活细胞中的生物合成机制，并与纯化的酶一起研究，以了解不同的PKS和“剪裁”成分在构建最终活性产品中的作用。它将探索该途径不同部分进行的反应及其产生新化合物的灵活性。这些将用于筛选可能用作预防或治疗药物的新生物活性。

Biological systems build complex molecules for many different purposes - building blocks for cells, and supracellular structures, the catalytic and energy storage systems that drive living cells, the messenger molecules that allow communication and information storage within and between organisms and finally the molecules that allow defence or aggression against other organisms. Mankind has learnt to exploit many of these natural compounds, not least those that act as antibiotics. One class of compounds, the polyketides, are of great importance because they include many molecules with a great diversity of structures which cover a whole range of useful activities - not just antibacterials, but also antifungals, anticancer and anticholesterol agents, to name just a few. Typically, the molecular 'backbones' of these compounds are made by joining simple building blocks on an assembly line, each building block being added by a separate 'module' that also processes the new segment to one of a number (normally three) of modifications (known as the Type I PKS pathway). The resulting molecular chain can be of different lengths and combinations of modifications and can then be decorated with different side chains to produce a unique product ('tailoring'). However, an increasing number of atypical pathways are being uncovered that appear to use additional mechanisms not yet defined. These provide ways of producing new structures in a controlled way. One such pathway, found in Pseudomonas fluorescens, synthesises the clinically important antibiotic mupirocin. It is most active against Gram positive bacteria and is particularly used against MRSA (Methicillin Resistant Staphylococcus aureus), one of the most dangerous 'superbugs'. Biosynthesis of mupirocin involves an atypical Type I PKS along with a large number of 'tailoring' enzymes some of which we have discovered act in tandem with the PKS in building the backbone of mupirocin. This is in contrast to typical type I PKS modules which within themselves contain all the information needed to build the backbone. This project integrates microbial molecular genetics, biochemistry and chemistry to study the biosynthetic machinery both in living cells and with purified enzymes to understand the role of the different PKS and 'tailoring' components in building the final active product. It will explore the reactions carried out by different parts of the pathway and their flexibility to produce new compounds. These will be made available for screening for new biological activities that may be of use as prophylactic or therapeutic agents.