Discovery and functional study of a bioactive peptide QUB-1892 from the defensive skin secretion of The Edible Frog (Pelophylax eculentus)

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.