Trypsin resistance of a decapeptide KISS1R agonist containing an Nω-methylarginine substitution

Abstract Metastin/kisspeptin is an amidated peptide with 54 amino acid residues isolated from human placental tissues as a ligand of the orphan G-protein-coupled receptor KISS1R that is expressed throughout the central nervous system and in a variety of endocrine and gonadal tissues. Compared to the full-length metastin protein, the N-terminal truncated peptide metastin(45–54) has 3–10 times higher receptor affinity and enhanced ability to increase intracellular calcium concentration which is essential for activation of protein kinases involved in intracellular signaling in a number of pathways that affect reproduction and cell migration. However, metastin(45–54) is rapidly inactivated in serum. In this study, we designed and synthesized a number of metastin(45–54) analogs and evaluated their agonistic activity and trypsin resistance. Among analogs with substitutions of arginine at position 53, N ω - methylarginine analog 8 showed 3-fold more potent agonistic activity compared with metastin(45–54). Furthermore, analog 8 was shown to resist trypsin cleavage between positions 53 and 54. This substitution may be useful in the development of other Arg-containing peptides for which the avoidance of cleavage is desired.