V型羊毛硫肽雷可肽的抑菌机制

【背景】雷可肽(Lexapeptide)为首例V型羊毛硫肽家族化合物,具有较好的抗革兰氏阳性菌活性,对耐甲氧西林金黄色葡萄球菌(Methicillin-Resistant Staphylococcus aureus,MRSA)和表皮葡萄球菌(Methicillin-Resistant Staphylococcus epidermidis,MRSE)的抑制作用强于广泛应用的食品防腐剂乳酸链球菌素,其对pH和高温的稳定性也优于乳酸链球菌素,具有较好的应用前景。由于抑菌机制不明确,限制了雷可肽的开发应用。【目的】探究雷可肽抑菌作用特征以及作用机制,为雷可肽开发应用奠定基础。【方法】通过菌落计数法与Mg2+试验表征雷可肽抑菌动力学曲线;采用流式细胞仪和透射电子显微镜研究雷可肽在靶细胞表面的成孔性;利用高效液相色谱与基质辅助激光解吸电离的时间飞行质谱分析雷可肽处理对革兰氏阳性菌肽聚糖前体积累的影响。【结果】雷可肽在抑菌动力学上与乳酸链球菌素没有显著差别,但在更宽的Mg2+浓度范围内仍可保持抑菌活性。雷可肽处理后的细胞具有透过荧光染料的能力,生物型透射电镜观察到细胞发生破损。此外,在雷可肽作用后的细胞中检测到肽聚糖合成的前体尿嘧啶核苷二磷酸-N-乙酰胞壁酸五肽。【结论】雷可肽能够通过抑制细胞壁肽聚糖生物合成并造成细胞损伤进而获得通透性,以此来抑制革兰氏阳性菌生长。

The antibacterial mode of action of lexapeptide

Background] Lexapeptide is the first member of the class V lanthipeptide family. In vitro bioassay indicated that lexapeptide has remarkable antibacterial activity against various G⁺ bacteria, and shows stronger activity against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) than nisin. Lexapeptide also exhibits better thermo-stability and pH-stability than nisin. The mode of actions of lexapeptide remains uncovered, hindering its potential application. Objective] Through investigation into the antibacterial mode of action of lexapeptide to lay the foundation for its further application. Methods] The antibacterial kinetics of lexapeptide was characterized by colony-forming unit (CFU) counting and magnesium ion assay. The pore forming ability of lexapeptide was assessed by flow cytometry (FCM) and transmission electron microscopy (TEM). High performance liquid chromatography (HPLC) and matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used to analyze lexapeptide''s effect on the accumulation of peptidoglycan biosynthetic precursor in G⁺ bacteria. Results] Compared to nisin, the antibacterial activity of lexapeptide was less sensitive to the inhibition by magnesium ion. Bacterial cells treated with lexapeptide gained permealiability to fluorescent dye. Damaged morphology of those cells was observed with TEM. A peptidoglycan biosynthetic precursor, UDP-NAcMur-pentapeptide, was determined in the lexapeptide-treated cells.Conclusion] Lexapeptide inhibits the growth of G⁺ bacteria by inhibiting the biosynthesis of peptidoglycan in cell wall as well as permeabilizing the cell membrane.