使用含有二苯基酮之抑制劑作為細菌轉醣酶之光親和探針

Abstract

使用抗生素是一種常見的方式用以治療細菌引起的疾病，在多種能有效殺死細菌的機轉中，抑制細菌細胞壁的生合成擁有最佳的結果，一旦細菌的喪失了細胞壁，便失去了喪失承受外界嚴峻環境的能力。細菌的肽聚醣細胞壁是由透過轉醣酶與轉肽酶催化由單體lipid II聚合而成，盤尼西林與萬古黴素便是兩個有效的抗生素，盤尼西林透過抑制轉肽酶催化的交聯反應終止細胞壁的合成，而萬古黴素則透過與受質lipid II結合而使其與無法與酵素作用。在過去數十年間，抗生素的濫用已導致具有抗藥性的細菌出現，開發出新型態的抗生素已經成為現在的重要議題。 我們的研究主要針對細菌轉醣酶的抑制。轉醣酶屬於盤尼西林結合蛋白的一部分，屬於位在細胞膜的外側的膜蛋白。因此，抑制劑在與轉醣酶作用的過程中可面對較少的阻礙。此外，合成細胞壁的蛋白並不存在於哺乳動物的細胞之中，抑制劑可望面臨較少的副作用。 透過高通量篩選系統，中央研究院基因體研究中心的研究團隊發現一系列的水楊醯替苯胺衍生物具有對轉醣酶的抑制能力。其中一個具有二苯基酮的抑制劑可以透過激發光照射產生自由基而進行光親和標記。在此研究中，我們合成出該抑制劑進行光親和標記，再透過質譜分析以了解結合位置。為研究新型態抗生素提供更多資訊。

Using antibiotics is a common method for treatment of bacterial-induced diseases. Inhibiting the biosynthesis of bacterial cell wall is one of several mechanisms for antibiotics to eliminate bacteria. Under catalysis of transglycosylase (TGase) and transpeptidase (TPase), peptidoglycan cell wall is synthesized from the monomeric substrate, lipid II. Once bacterium cannot synthesize the cell wall, it loses the ability to sustain severe surrounding. Penicillin and vancomycin are two effective antibiotics. Penicillin kills bacteria by suppressing the TPase-catalyzed cross-link reaction, whereas vancomycin binds lipid II to block it from transpeptidation. In past decades, abuse of antibiotics has caused the occurrence of antibiotic-resistant bacteria. Developing new antibiotics becomes an important issue. Instead of targeting TPase, our research focuses on TGase inhibition. TGase belongs to penicillin-binding protein, which is a membrane protein located on the surface of bacteria, thus inhibitors can face less obstacles to access the enzyme. Besides, the enzymes involved in bacterial cell wall synthesis do not exist in human body, thus TGase inhibitors are expected to cause fewer side effects. By high throughput screening, a research team in the Genomics Research center of Academia Sinica found a series of salicylanilide-based compounds having potential to act as TGase inhibitors. One of the potential inhibitors contains a benzophenone moiety, which can be used to generate a radical by irradiation for photoaffinity labeling. We thus synthesize this salicylanilide-based compound to conduct the photoaffinity labeling experiment, and analyze the bound peptides by mass spectrometry to get more information about the binding mode. This study can inspire a new way to develop new antibiotics.