The discovery and functional study of a novel bioactive peptide, QUB-2561, from the defensive skin secretion of the Central American red-eyed leaf frog, Agalychnis callidryas.
Peptides are short amino acid chains with multiple bioactivities. Compared with other small molecular drug candidates, peptides are highly specific and not easy to induce side effects. Many antimicrobial peptides (AMPs) have been found in frog skin epidermal secretions, which usually have broad-spectrum antibacterial activities and are unlikely to induce drug resistance. In this study, a novel peptide QUB-2561 was found from the defensive skin secretion of the Central American red-eyed leaf frog, Agalychnis callidryas by “Shotgun” cloning. Because of the limited quantity of the secreted peptides, the peptide replicate was firstly synthesised via solid-phase peptide synthesis and validated by reversed-phase high performance liquid chromatography and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. The pure QUB-2561 was used to study the bioactivities. The results showed that QUB-2561 had potent antimicrobial effects on the Gram-positive bacterium, Staphylococcus aureus, the Gram-negative bacterium, Escherichia coli and the yeast, Candida albicans. The minimal inhibitory concentration and minimum bactericidal concentration of QUB-2561 against the three above microorganisms were both 2 µM, at which the haemolytic effect of QUB-2561 on horse red blood cells was only 2.53%. The study of the novel peptide QUB-2561 provided a lead template for developing natural peptides as potential therapeutic agents.
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