Safer Aminoglycoside Therapeutics by Biosynthetic Engineering

医院患者的细菌感染可导致败血症，由产生毒素的细菌对血液的压倒性感染会危及生命。目前正在开发的新抗生素很少，因此40多年前发现的现有抗生素庆大霉素很可能仍然是抗击败血症的重要支柱。不幸的是，使用庆大霉素确实存在危险：使用庆大霉素或相关抗生素治疗的患者中，有很大比例会出现急性肾功能衰竭(肾毒性)。该药物还可能导致不可逆转的听力损失(耳毒性)。治疗费用非常昂贵，因为必须密切监测患者，以将这些严重的副作用降至最低。人们一直在努力研究将庆大霉素的副作用降至最低的方法，例如通过改变给药策略；并了解肾脏和内耳受损的生化机制。不幸的是，所有临床上使用的庆大霉素都是化合物的混合物，不同批次的商业庆大霉素每种成分的含量都不同。单个组件可以小规模分离，但按所需规模进行分离在商业上并不可行。人们认为所有成分都是同等有效和同等毒性的，但在2006年，美国的研究人员重新测试了每一种主要成分(即C1、C1a、C2和C2a)，结果表明，令人惊讶的是，纯化的成分C2作为抗生素完全有效，但完全没有肾毒性(至少对大鼠)。这个项目的目的是在我们之前由MRC支持的研究的成功的基础上，旨在破译庆大霉素生物合成后期阶段的所有单独步骤。我们现在认为，通过发酵获得C2的最好前景是以商业上广泛存在的名为G418的前体为原料。然而，我们仍然需要了解关键的单个酶在这一部分途径中的作用。这种单组份庆大霉素的现成供应将鼓励潜在更安全的抗生素配方进行测试。由于庆大霉素和相关的氨基糖苷类药物也很有希望用于纠正某些人类遗传性疾病，如囊性纤维化和肌肉萎缩症Duchenne肌营养不良症，因此也可能有更广泛的医疗益处。

Bacterial infections in hospital patients can lead to sepsis, in which an overwhelming infection of the bloodstream by toxin-producing bacteria becomes life-threatening. Very few new antibiotics are being developed, and so the established antibiotic gentamicin, discovered over 40 years ago, is likely to remain a vital mainstay in efforts to combat sepsis. Unfortunately there are real dangers associated with its use: a large percentage of patients treated with gentamicin, or related antibiotics, develop acute kidney failure (nephrotoxicity). The drug can also cause irreversible hearing loss (ototoxicity). Treatment is very costly because patients have to be closely monitored to minimise these severe side-effects. Sustained efforts are being made to research ways of minimising the side-effects of gentamicin, by altering the dosing strategy for example; and to understand the biochemical mechanisms by which the kidney and the inner ear are damaged. Unfortunately all the gentamicin used clinically is a mixture of compounds and different batches of commercial gentamicin have different amounts of each component. The individual components can be separated on a small scale but it has not been commercially viable to do this on the scale needed. It was believed that all components were equally effective and equally toxic, but in 2006 researchers in the USA re-tested each of the main components (known as C1, C1a, C2, and C2a) and showed that, surprisingly, purified component C2 is fully effective as an antibiotic but not nephrotoxic at all (at least in rats). The aim of this project is to build on the success of our previous MRC-supported research aimed at deciphering all of the individual steps in the late stages of gentamicin biosynthesis. We now think that the best prospect for obtaining C2 by fermentation is to use as a feedstock the widely commercially available precursor called G418. However, we still need to deconvolute the role of key individual enzymes in this part of the pathway. The ready availability of such monocomponent gentamicins would encourage potentially safer formulations of the antibiotic to be tested. Since gentamicins and related aminoglycosides are also promising agents for the correction of certain human genetic diseases, such as cystic fibrosis and the muscle-wasting disease Duchenne muscular dystrophy, there could be wider medical benefits too.