D-form KLKLLLLLKLK-NH peptide exerts higher antimicrobial properties than its L-form counterpart via an association with bacterial cell wall components.

The antimicrobial peptide KLKLLLLLKLK-NH was developed based on sapesin B, and synthesized using D-amino acids. Biochemical properties of the D-form and L-form KLKLLLLLKLK-NH peptides were compared. In order to limit the effects due to bacterial resistance to proteolysis, antimicrobial activities of the peptides were evaluated after short-term exposure to bacteria. D-form KLKLLLLLKLK-NH exhibited higher antimicrobial activities than L-form KLKLLLLLKLK-NH against bacteria, including Staphylococcus aureus and Escherichia coli. In contrast, both the D-form and L-form of other antimicrobial peptides, including Mastoparan M and Temporin A, exhibited similar antimicrobial activities. Both the D-form KLKLLLLLKLK-NH and L-form KLKLLLLLKLK-NH peptides preferentially disrupted S. aureus-mimetic liposomes over mammalian-mimetic liposomes. Furthermore, the D-form KLKLLLLLKLK-NH increased the membrane permeability of S. aureus more than the L-form KLKLLLLLKLK-NH. Thus suggesting that the enhanced antimicrobial activity of the D-form was likely due to its interaction with bacterial cell wall components. S. aureus peptidoglycan preferentially inhibited the antimicrobial activity of the D-form KLKLLLLLKLK-NH relative to the L-form. Furthermore, the D-form KLKLLLLLKLK-NH showed higher affinity for S. aureus peptidoglycan than the L-form. Taken together, these results indicate that the D-form KLKLLLLLKLK-NH peptide has higher antimicrobial activity than the L-form via a specific association with bacterial cell wall components, including peptidoglycan.