Molecular cloning, structural characterisation and functional study of bioactive peptides from <i>Odorrana versabilis</i> skin secretion

Furthermore, we confirmed the importance of the Rana box and net charge threshold from the results of NR-BOV, AK-BOV, LRK-BOV and FR-BOV. <br><br>In Chapter 4, we successfully isolated and identified a novel trypsin inhibitor peptide, Kunitzin-OV2, and its derivative, F9-Kunitzin-OV2, showed inhibition of chymotrypsin. However, the difficulty of Kunitzin-OV2 and its analogue in entering cells or reacting with cell membranes rendered them functionally inactive.

It was hypothesised that Kunitzin-OV2 acted on intracellular targets and that its effective activity requires additional 'carrier' assistance to achieve this. Therefore, in Chapter 5, cationic cell-penetrating peptides (CPPs) were used to conjugate to parent peptides. The results showed that the conjugation was effective and non-toxic.

All conjugates showed superior antimicrobial activity while also selectively targeting cancer cells without harming normal cells. The analogue with the most outstanding effect was LMWP-F9-Kunitzin-OV2 (LMWP-F9-KOV2), which enhanced the bactericidal capacity of the parent peptide without increasing toxicity, especially against E. coli, and it has also was shown to kill H157 cancer cells in a dose-dependent manner by inducing apoptosis.

This cationic CPP conjugation to bioactive peptides is a new idea for peptide drug design, which could provide a practical aid for the bioavailability and targeting of peptides.<br><br><i>Thesis is embargoed until 31 July 2028.</i>