The global health threat surrounding bacterial resistance has resulted in antibiotic researchers shifting their focus away from 'traditional' antibiotics and concentrating on other antimicrobial agents, including antimicrobial peptides. These low molecular weight "mini-proteins" exhibit broad-spectrum activity against bacteria, including multi-drug resistant strains, viruses, fungi and protozoa and constitute a major element of the innate-immune system of many multicellular organisms. Some naturally occurring antimicrobial peptides are lipidated and/or glycosylated and almost all antimicrobial peptides in clinical use are either lipopeptides (Daptomycin and Polymyxin E and B) or glycopeptides (Vancomycin). Lipidation, glycosylation and PEGylation are an option for improving stability and activity in serum and for reducing the rapid clearing via the kidneys and liver. Two broad-spectrum antimicrobial peptides NH2-RIRIRWIIR-CONH2 (A1) and NH2-KRRVRWIIW-CONH2 (B1) were conjugated via a linker, producing A2 and B2, to individual fatty acids of C8, C10, C12 and C14 and in addition, A2 was conjugated to either glucose, N-acetyl glucosamine, galactose, mannose, lactose or polyethylene glycol (PEG). Antimicrobial activity against two Gram-positive strains (methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococcus faecalis (VRE)) and three Gram-negative strains (Salmonella typhimurium, E. coli and Pseudomonas aeruginosa) were determined. Activity patterns for the lipidated versions are very complex, dependent on sequence, bacteria and fatty acid. Two reciprocal effects were measured; compared to the parental peptides, some combinations led to a 16-fold improvement whereas other combinations let to a 32-fold reduction in antimicrobial activity. Glycosylation decreased antimicrobial activity by 2 to 16-fold in comparison to A1, respectively on the sugar-peptide combination. PEGylation rendered the peptide inactive. Antimicrobial activity in the presence of 25% human serum of A1 and B1 was reduced 32-fold and 8-fold, respectively. The longer chain fatty acids almost completely restored this activity; however, these fatty acids increased hemolytic activity. B1 modified with C8 increased the therapeutic index by 2-fold for four bacterial strains. Our results suggest that finding the right lipid-peptide combination can lead to improved activity in the presence of serum and potentially more effective drug candidates for animal studies. Glycosylation with the optimal sugar and numbers of sugars at the right peptide position could be an alternative route or could be used in addition to lipidation to counteract solubility and toxicity issues.

中文翻译：

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脂质化和糖基化对短阳离子抗菌肽的影响。

围绕细菌耐药性的全球健康威胁已导致抗生素研究人员将重点从“传统”抗生素转移到了其他抗菌剂上，包括抗菌肽。这些低分子量的“微型蛋白质”对细菌具有广谱活性，包括多重耐药菌株，病毒，真菌和原生动物，并且是许多多细胞生物的先天免疫系统的主要组成部分。一些天然存在的抗菌肽被脂化和/或糖基化，临床上几乎所有的抗菌肽都是脂肽（达托霉素和多粘菌素E和B）或糖肽（万古霉素）。脂化 糖基化和聚乙二醇化是改善血清中的稳定性和活性以及减少通过肾脏和肝脏的快速清除的一种选择。通过接头将两个广谱抗菌肽NH2-RIRIRWIIR-CONH2（A1）和NH2-KRRVRWIIW-CONH2（B1）结合，生成A2和B2，分别与C8，C10，C12和C14的各个脂肪酸结合，此外，将A2缀合至葡萄糖，N-乙酰基葡糖胺，半乳糖，甘露糖，乳糖或聚乙二醇（PEG）。确定了对两种革兰氏阳性菌株（耐甲氧西林的金黄色葡萄球菌（MRSA）和耐万古霉素的粪肠球菌（VRE））和三种革兰氏阴性菌株（鼠伤寒沙门氏菌，大肠杆菌和铜绿假单胞菌）的抗菌活性。脂化版本的活性模式非常复杂，具体取决于序列，细菌和脂肪酸。测量了两个相互影响。与亲本肽相比，某些组合导致抗微生物活性降低16倍，而其他组合导致抗微生物活性降低32倍。与A1相比，糖基化对糖肽组合的糖基化作用使抗菌活性降低了2到16倍。聚乙二醇化使肽失去活性。在存在25％的人血清A1和B1的情况下，抗菌活性分别降低了32倍和8倍。较长链的脂肪酸几乎完全恢复了这种活性。然而，这些脂肪酸增加了溶血活性。用C8修饰的B1对四种细菌菌株的治疗指数提高了2倍。我们的结果表明，在血清中存在的情况下，找到正确的脂肽组合可以改善活性，并可能在动物研究中使用更有效的候选药物。具有最佳糖和正确肽位置糖数量的糖基化可以是替代途径，也可以用于脂化以抵消溶解性和毒性问题。