Discovery and functional study of a bioactive peptide QUB-1892 from the defensive skin secretion of The Edible Frog (Pelophylax eculentus)
Amphibian skin secretions not only act as mere tegmental lubrication but also have many more complex functions such as seen in their antimicrobial activity. In this thesis, a novel Kunitz-like trypsin inhibitor was isolated from the skin secretion of Pelophylax kl esculentus and was named QUB-1892. The mature peptide was synthesised by solid-phase peptide synthesis (SPPS). RP-HPLC and MALDI-TOF MS were used to purify and analyse the mature peptide. Its minimal inhibitory concentration (MIC) was obtained by using different micro-organisms and its haemolytic activity was tested by the use of horse red blood cells. The results of antimicrobial experiments showed that QUB-1892 was active only against E.coli with a MIC of 256 μM. Trypsin inhibitor assays revealed that QUB-1892 had inhibitory action against trypsin with a Ki value of 3.6 µM. Also, QUB-1892 had low haemolytic activity. The outstanding ability of QUB-1892 to inhibit trypsin gives this novel peptide potential for use in the development of new drugs for clinical application.
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