PPF-BBI peptide

PPF-BBI is a novel bioactive Bowman-Birk type inhibitory hexadecapeptide of the Ranacyclin family from the defensive skin secretion of the Fukien gold-striped pond frog, Pelophlax plancyi fukienesis. PPF-BBI was shown to possess a potent trypsin and tryptase inhibitory activity with a high specificity. A better antimicrobial activity was observed when P16 of PPF-BBI was replaced by Lys, and the addition of the cell-penetrating peptide Tat48–56 resulted in a peptide with a strong antifungal activity. The specificity of inhibition is determined by whether the P1 position residue can fit into the S1 pocket of protease. Based on previous reports, Lys as the P1 position is optimal for trypsin inhibition, and Phe is optimal for chymotrypsin. Similarly, PPF-BBI, which has a Lys at the P1 site, showed a strong trypsin inhibitory activity and substitution of the Lys at the P1 position, with Phe leading to the elimination of the trypsin inhibition and giving rise to a chymotrypsin inhibitory activity. In the tryptase activity assay, PPF-BBI displayed a mild potency toward tryptase with a Ki value of 30.52 µM. K16-PPF-BBI shows a three-fold better inhibition with a Ki value of 9.67 µM