Characterisation and exploitation of a promiscuous non-ribosomal peptide cyclase

大多数临床使用的抗生素来自链霉菌和其他密切相关的土壤细菌产生的天然产物。这些药物最初是在1940年至1960年抗生素发现的“黄金时代”被发现并引入临床的。在过去的半个世纪里，由于滥用，这些制剂的效用已经被侵蚀。因此，现在迫切需要发现新的抗生素来治疗耐药细菌感染。人们对抗菌剂耐药性的担忧与日俱增，再加上未能从大量合成化合物的筛选中找到新的线索，导致人们对天然产物的发现重新产生了兴趣。不幸的是，绝大多数微生物还没有培养出来，对于那些已经培养出来的微生物来说，他们的天然产物只有一小部分是在实验室里生产的。克服这一问题的传统方法通常依赖于对生产有机体进行耗时的基因改造，或者使用鲜为人知的“激发子”化合物来启动生产。这种方法的瓶颈是，可能会在一个生物合成途径上花费大量时间，而该途径的产品永远不会被生产出来，或者不是抗生素。此外，即使成功地激活了抗生素途径，发现先导化合物也只是药物发现的第一阶段。许多抗生素都来自一类被称为非核糖体多肽的微生物天然产物。一旦确定了令人兴奋的前景，未来的发展最终取决于它的可达性。微生物发酵很少提供足够的化合物来推进，因此通常使用化学合成来生产测试发现线索临床潜力所需的数量，重要的是类似物的化学多样性。这里的问题是，绝大多数非核糖体多肽是环状的，环化反应通常非常有问题，产生的最终化合物的产率很低。在自然界中，环化反应是由生物合成途径的一部分进行的，称为硫代酯酶结构域。我们最近发现了一种新的环化酶，它与它所循环的多肽底物是混杂的。这是令人兴奋的，我们想了解这种酶是如何工作的，这样我们就可以利用它的生物技术潜力。例如，改进抗生素的化学合成。我们相信，这最终可以帮助更多的药物进入临床，可能会使它们更便宜，更广泛地获得。

The majority of clinically used antibiotics are derived from natural products produced by Streptomyces species and other closely related soil bacteria. These drugs were primarily discovered and introduced into the clinic during a 'golden era' of antibiotic discovery that spanned 1940-1960. The utility of these agents has been eroded over the last half-century due to misuse. As a consequence, there is now an urgent need to discover new antibiotics to treat drug resistant bacterial infections. Growing concerns about resistance to antibacterial agents combined with the failure to find new leads from the screening of large libraries of synthetic compounds has led to a renewed interest in natural products discovery. Unfortunately, the overwhelming majority of microbes have yet to be cultured, and for those that have, only a small fraction of their natural products are produced in the laboratory. Conventional approaches to overcome this problem, typically rely upon time consuming genetic modification of the producing organism or the use of poorly understood 'elicitor' compounds to switch on production. The bottleneck with this approach is the fact that a large amount time can be spent on one biosynthetic pathway whose product could never be produced or is not an antibiotic. Moreover, even if success in activating an antibiotic pathway is achieved, discovery of a lead compound is only the first stage of drug discovery. Many antibiotics are derived from a class of microbial natural products called non-ribosomal peptides. Once an exciting prospect is identified, future development is ultimately dictated by its accessibility. Microbial fermentation rarely provides sufficient compound to move forward and therefore chemical synthesis is typically used to produce the quantity, and importantly, the chemical diversity of analogues necessary for testing the clinical potential of a discovery lead. The problem here is that the vast majority of non-ribosomal peptides are cyclic and cyclisation reactions are typically very problematic and produce a low yield of the final compound. In nature, the cyclisation reaction is carried out by a part of the biosynthetic pathway called a thioesterase domain. We recently identified a novel cyclase enzyme, which is promiscuous with respect to the peptide substrates it cyclises. This is exciting and we want to understand how this enzyme works so we can harness its potential for biotechnology. For example, to improve chemical synthesis of antibiotics. We believe this could ultimately help more medicines reach the clinic, possibly making them less expensive and more widely available.