A bioactive peptide from the frog skin secretion of Pelophylax nigromaculatus GAPKGCWTKSYPPKPCS-NH2

The precursor was obtained from the Pelophylax nigromaculatus skin secretion by employing molecular cloning. The corresponding mature peptide, namely QUB-1804, was identified by bioinformatics approach from this cloned biosynthetic precursor-encoding cDNA sequence.

Subsequently, the chemically-synthesised replicate was subjected to a series of bioassays. It was found that QUB-1804 is a Bowman-Birk-type protease inhibitor which belongs to ranacyclin family. It has respectively trypsin inhibitory activity with Ki value of 0.373 μM. But QUB-1804 does not possess significant antimicrobial activity on three model micro-organisms: Gram-positive bacterium (S. aureus), Gram-negative bacterium (E. coli) and an opportunistic yeast bacterium (C. albicans).