Antimicrobial activity and stability of the d-amino acid substituted derivatives of antimicrobial peptide polybia-MPI

Yanyan Zhao, Min Zhang, Shuai Qiu, Jiayi Wang, Jinxiu Peng, Ping Zhao, Ranran Zhu, Hailin Wang, Yuan Li, Kairong Wang, Wenjin Yan, Rui Wang

Antimicrobial peptide has the potential to be developed as new kind of antimicrobial agents with novel action mechanism. However, the susceptibility to protease is a drawback for potential peptides to be clinical used. D-amino acid substitution can be one way to increase the proteolytic stability of peptides. In the present study, we synthesized the D-lysines substituted analog (D-lys-MPI) and the D-enantiomer of polybia-MPI (D-MPI) to improve the proteolytic resistance of polybia-MPI. Our results showed that, the stability of its D-amino acid partially substituted analog D-lys-MPI was increased. However, it lost antimicrobial activity at the tested concentration with the loss of α-helix content. As shown in the CD spectra, after substitution, the spectra of D-MPI is symmetrical to MPI, indicated it turned into left hand α-helical conformation. Excitingly, the stability of D-MPI toward the tested protease was improved greatly. Notably, the antimicrobial activity of D-MPI was comparable to its L-counterpart MPI, even improved. In addition, the hemolytic activity of D-MPI was lowered. This also indicated that the action target of antimicrobial peptide polybia-MPI was not chiral specific. So, D-MPI may offer a therapeutic strategy to defend the infection of microbes, considering its stability to protease and relatively lower cytotoxicity to human erythrocytes.