Safer Aminoglycoside Therapeutics by Biosynthetic Engineering

住院病人的细菌感染可导致败血症，在这种情况下，产生毒素的细菌对血液的压倒性感染会危及生命。很少有新的抗生素被开发出来，因此40多年前发现的现有抗生素庆大霉素可能仍然是对抗败血症的重要支柱。不幸的是，使用庆大霉素确实存在危险：大部分接受庆大霉素或相关抗生素治疗的患者出现急性肾衰竭（肾毒性）。这种药物还会导致不可逆的听力损失（耳毒性）。治疗费用非常昂贵，因为必须密切监测患者，以尽量减少这些严重的副作用。正在作出持续努力，研究诸如通过改变给药策略来尽量减少庆大霉素副作用的方法；了解肾脏和内耳受损的生化机制。不幸的是，临床上使用的所有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不同。单个组件可以在小范围内分离，但在商业上不可行，这样做需要的规模。人们认为所有的成分都是同样有效和同样毒性的，但在2006年，美国的研究人员重新测试了每个主要成分（称为C1， C1a， C2和C2a），并显示，令人惊讶的是，纯化的成分C2作为抗生素是完全有效的，但根本没有肾毒性（至少在大鼠身上）。该项目的目的是建立在我们之前mrc支持的研究的成功基础上，旨在破译庆大霉素生物合成后期的所有单个步骤。我们现在认为，通过发酵获得C2的最佳前景是使用广泛商用的前体G418作为原料。然而，我们仍然需要解开关键单个酶在这部分途径中的作用。这种单组分庆大霉素的现成可用性将鼓励对可能更安全的抗生素配方进行测试。由于庆大霉素和相关氨基糖苷类药物也有望用于纠正某些人类遗传疾病，如囊性纤维化和肌肉萎缩疾病杜氏肌营养不良症，因此也可能有更广泛的医疗效益。

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.