Research Fellow of the Japan Society for the Promotion of Science, Sakyo-ku, Kyoto 606-8502, Japan.
Chem Biol Drug Des. 2012 Nov;80(5):725-33. doi: 10.1111/cbdd.12012. Epub 2012 Sep 10.
Antimicrobial peptides are promising antibiotics as they possess strong antimicrobial activity and very broad spectra of activity. However, administration of an antibiotic with a very broad spectrum of activity disrupts normal microflora and increases the risks of other fatal infections. To solve the problem, we designed a novel antimicrobial peptide that is activated by virulent proteases of pathogenic organisms. We constructed a peptide composed of three domains, namely an antimicrobial peptide (lactoferricin) as the active center, a protective peptide (magainin intervening sequence) that suppresses antimicrobial activity, and a specific linker that joins these two components and is efficiently cleaved by virulent proteases. We utilized Candida albicans as a model organism that produces secreted aspartic proteases as a virulence attribute. We screened for a peptide sequence efficiently cleaved by secreted aspartic proteases isozymes and identified a GFIKAFPK peptide as the most favorable substrate. Subsequently, we chemically synthesized a peptide containing the GFIKAFPK sequence. The designed peptide possessed no antimicrobial activity until it was activated by secreted aspartic proteases isozymes. Furthermore, it demonstrated selective antimicrobial activity against C. albicans, but not against Saccharomyces cerevisiae. A designed peptide like the one described in this study may protect normal microflora, resulting in enhanced safety as a therapeutic.
抗菌肽是很有前途的抗生素，因为它们具有很强的抗菌活性和非常广泛的活性谱。然而，使用具有非常广泛活性谱的抗生素会破坏正常的微生物群落，并增加其他致命感染的风险。为了解决这个问题，我们设计了一种新型的抗菌肽，它可以被病原体的毒性蛋白酶激活。我们构建了一种由三个结构域组成的肽，即作为活性中心的抗菌肽（乳铁蛋白）、抑制抗菌活性的保护肽（防御素 intervening 序列）和一个特异性接头，它将这两个组件连接起来，并能被毒性蛋白酶有效地切割。我们利用白色念珠菌作为一个模型生物，它产生分泌天冬氨酸蛋白酶作为一种毒力属性。我们筛选了能被分泌天冬氨酸蛋白酶同工酶有效切割的肽序列，并鉴定出一个 GFIKAFPK 肽作为最有利的底物。随后，我们化学合成了一种含有 GFIKAFPK 序列的肽。该设计的肽在被分泌天冬氨酸蛋白酶同工酶激活之前没有抗菌活性。此外，它对白色念珠菌表现出选择性的抗菌活性，但对酿酒酵母没有。像本研究中描述的那样的设计肽可以保护正常的微生物群落，从而提高治疗的安全性。
