基于结核杆菌细胞壁合成途径关键酶—UDP-半乳糖变异酶抑制剂的设计、合成及抗结核活性研究

Tuberculosis (TB) remains one of the most world’s deadliest infectious diseases. Mycobacterium tuberculosis (Mtb), the causative agent of TB, is responsible for million fatalities every year, and treatment of TB is complicated by the emergence of multidrug-resistant TB (MDR-TB). Thus, new anti-tuberculosis drugs with novel mechanism of action are urgently needed to eradicate TB. The inhibition of the Mtb cell envelope constitutes a robust therapeutic strategy because it is essential for mycobacterial viability and pathogenesis. Galactofuranose (Galf) is present in glycans critical for the virulence and viability of several pathogenic microbes, including Mycobacterium tuberculosis. The enzyme UDP-galactopyranose mutase (UGM) catalyzes the reversible interconversion of UDP-galactopyranose (UDP-Galp) and UDP-Galf, yet the Galf and UGM are in mammalians, inhibition of this enzymatic isomerization represents an attractive therapeutic strategy.. In our previous study, we screened a large seires of natural products and their derivatives by a fluorescence polarization assay. One specific compound, rosmarinic acid, isolated from Salvia cavaleriei Levl., exhibited moderate MtUGM inhibitory activity. To discover a more potent inhibitor, the bioisosteric replacement of structural elements of rosmarinic acid will be exploited to generate a 1st generation of analogues. Bioisosteric replacement of the ester by an amide, is considered as a priority because ester isosteres have frequently been developed to address metabolism issues since esters can be rapidly cleaved in vivo, while amide bond enhance the stability. For the above reasons, we therefore postulated that potent and selective inhibitors of UGM could be discovered based on an amide bond construction. A leading compound—enamide was discovered via a new combinatorial in situ screening technology. In order to develop more potent UGM inhibitors, a number of derivatives were rational designed, allowed a structure–activity relationship analysis. The binding mode was predicted by means of molecular modeling software AutoDock Vina and also validated by Lineweaver-Burk kinetic study.. The main objective of this project is to obtain 1-2 more potent lead compounds (prodrugs) with potent UGM inhibitory activity for the further new anti-tuberculosis drugs development.

结核病是我国乃至世界范围内严重危害人类健康的重大疾病之一。具有全新作用机制及作用靶标的抗结核新药研发历来是研究热点。UDP—半乳糖变异酶（UDP-Galactopyranose Mut-ase, UGM）是结核分枝杆菌细胞壁中半乳呋喃聚糖前体—UDP-Galf生物合成的关键酶之一，是一个全新且已确证的抗结核药物靶标。本项目前期发现来源于民族药中的迷迭香酸具有较好UGM抑制活性，因其母体结构中存在酯键而致使其稳定性不佳，故设想根据生物电子等排原理引入稳定性更好的酰胺键来重新构建该苗头化合物。本项目拟采用自主开发的“原位筛选-荧光偏振”技术对不同的片段组合（>500）进行高通量筛选，进一步借助分子对接、基于片段的药物设计对先导化合物进行结构优化，并对所获得的衍生物分别在酶水平和菌株水平上进行抗结核活性评价，以期获得活性更高的先导化合物。本项目的开展将为开发具有较好前景的抗结核候选药物奠定基础。

结核病是我国乃至世界范围内严重危害人类健康的重大疾病之一。UDP—半乳糖变异酶（UDP-Galactopyranose Mutase,UGM）是结核分枝杆菌细胞壁中半乳呋喃聚糖前体—UDP-Galf生物合成的关键酶之一，是一个全新且已确证的抗结核药物靶标。本项目针对前期发现的UDP-半乳糖变异酶（UGM）抑制剂迷迭香酸，因其母体结构中存在酯键而致使其稳定性不佳，为改善其稳定性，通过生物电子等排策略，引入稳定性较好的酰胺键来重新构建该化合物。本项目自主建立了一个UGM抑制剂高通量的筛选平台——原位筛选-荧光偏振，对不同的片段组合进行高通量筛选，得到一系列苗头化合物。进一步借助分子对接、基于片段的药物设计对先导化合物进行结构优化，并对所获得的衍生物分别在酶水平和菌株水平上进行抗结核活性评价。设计合成的目标化合物表现出显著的抑制活性，Kd值均达到了微摩尔级，与目前文献报道的最好抑制剂活性相当。结果表明引入生物电子等排策略，用酰胺键代替迷迭香酸的酯键具有普适性，解决迷迭香酸在体内代谢的不稳定性，同时增强选择性。本项目的开展为开发具有较好前景的抗结核候选药物奠定基础。

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