Hylambatin (Hyl)

Hylambatin (Hyl), a dodecapeptide isolated from the skin of the African frog, Hylambates maculatus. Hylambatin and its 12 fragments were tested in the guinea-pig ileum preparation for contractile activities. All fragments except 3 had contractile activities. The C-terminal fragment as short as the octapeptide sequence was at least as active as the parent molecules. The heptapeptide fragment (Hyl6-12) and the hexapeptide fragment (Hyl7-12) were less active and the C-terminal pentapeptide fragment (Hyl8-12) and the N-terminal hexapeptide fragment (Hyl1-6) were much less active. The N-terminal pentapeptide fragment (Hyl1-5) and the N-terminal fragment from which the N-terminal Asp or Asp-Pro residues were removed (Hyl2-6, Hyl3-6), were inactive at doses used. Tachykinins are active peptides which excite neurons, evoke behavioral responses, are potent vasodilators and secretagogues, and contract many smooth muscles.