Isolation and amino acid sequences of alytesin and bombesin, two analogous active tetradecapeptides from the skin of European discoglossid frogs

Abstract

Crude methanol extracts of fresh skins of the European discoglossid frogs Alytes obstetricans, Bombina bombina, and Bombina variegata were subjected to chromatography on alumina columns and to gel filtration on Sephadex columns. The active constituents of these extracts, the peptides alytesin and bombesin, were obtained in pure form. Acid hydrolysis, digestion with trypsin and chymotrypsin, and group determination experiments demonstrated that alytesin and bombesin are tetradecapeptides differing only in the second and sixth residues from the NH 2-terminus. Synthesis, carried out only for bombesin, has confirmed the proposed sequence. The similarity between the structure of alytesin and bombesin on the one hand and that of ranatensin from Rana pipiens on the other is noted and discussed.