title: Antimicrobial activity and mechanism of action of a novel cationic α-helical octadecapeptide derived from α-amylase of rice.
abstract: AmyI-1-18, an octadecapeptide derived from α-amylase (AmyI-1) of rice (Oryza sativa L. japonica), is a novel cationic α-helical antimicrobial peptide (AMP) that contains two lysine and two arginine residues. The antimicrobial activity of AmyI-1-18 against human pathogens was quantitatively evaluated using a chemiluminescence method that measures ATP derived from viable cells. Of the ten kinds of human pathogens, AmyI-1-18 exhibited antimicrobial activity against nine. Its 50% growth-inhibitory concentrations (ICs50 ) against Porphyromonas gingivalis, Propionibacterium acnes, Pseudomonas aeruginosa, Candida albicans, and Streptococcus mutans were 13, 19, 50, 64, and 77 μM, respectively. AmyI-1-18 had little or no hemolytic activity even at 500 μM, and showed negligible cytotoxicity up to 1200 μM. The degree of 3,3'-dipropylthiadicarbocyanine iodide release from P. gingivalis cells induced by the addition of AmyI-1-18 was significantly lower than that induced by the addition of melittin. Flow cytometric analysis showed that the percentages of P. aeruginosa, S. mutans, and C. albicans cells stained with propidium iodide (PI), a DNA-intercalating dye, were 89%, 43%, and 3%, respectively, when AmyI-1-18 was added at a concentration equal to its 4×IC50 . Therefore, the antimicrobial activity of AmyI-1-18 against P. aeruginosa and S. mutans appears to be mainly attributable to its membrane-disrupting activity. In contrast, its antimicrobial activity against P. gingivalis and C. albicans most likely depends upon interactions with intracellular targets other than their cell membranes. Collectively, these results indicate that AmyI-1-18 is useful as a safe and potent AMP against the pathogens described above in many fields of healthcare.
authors.affiliation: Department of Materials Science and Technology, Graduate School of Science and Technology, Niigata University, Niigata, 950-2181, Japan; Center for Transdisciplinary Research, Niigata University, Niigata, 950-2181, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Taniguchi
authors.forename: Akihito
authors.initials: A
authors.lastname: Ochiai
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Takahashi
authors.forename: Shun-ichi
authors.initials: S
authors.lastname: Nakamichi
authors.forename: Takafumi
authors.initials: T
authors.lastname: Nomoto
authors.forename: Eiichi
authors.initials: E
authors.lastname: Saitoh
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Kato
authors.forename: Takaaki
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry* / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D012275:Oryza / Q000201:enzymology*; D016966:Porphyromonas gingivalis / Q000187:drug effects; D011425:Propionibacterium acnes / Q000187:drug effects; D017433:Protein Structure, Secondary; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D013329:Structure-Activity Relationship; D000516:alpha-Amylases / Q000737:chemistry*
chemical_list: D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D000516:alpha-Amylases
keywords: antimicrobial peptide; cationic α-helical peptide; human pathogens; intracellular targets; membrane-disrupting activity