Characterization of tryptolinophyllins from the treefrog Boana boans expands the structural and functional diversity of the trypytophyllin family of peptides.

Authors

Benjamin Lefranc, Laurent Coquet, Alexis Dougha, Hervé Meudal, Théophile Renwa, Nicolas Nalpas, Guillaume Gabant, Christophe Dubessy, Attilio Di Maio, Pierre Tufféry, Karine Loth, J Michael Conlon, Jérôme Leprince

Published in

Scientific reports. Jun 23, 2026. Epub Jun 23, 2026.

Abstract

Amphibian skin secretions constitute a rich source of bioactive peptides whose structural diversity is often amplified by post-translational modifications. In this study, we report the discovery and comprehensive characterization of a post-translational modification that has not been described previously in peptides from a vertebrate. Tryptophyllins are a heterogeneous group of short, tryptophan- and proline-containing peptides widely distributed among anuran species and are thought to contribute to skin protection against oxidative and UV-induced damage. Two peptides derived from tryptophyllins, termed tryptolinophyllins, were isolated from skin secretions of the giant gladiator treefrog Boana boans. They are distinguished by the presence of an N-terminal (S)-tryptoline-3-carboxylic acid (Tpi) residue, resulting from the conversion of tryptophan into a tetrahydro-β-carboline moiety via a Pictet-Spengler-type reaction. The primary structures of two tryptolinophyllins were elucidated by high-resolution tandem mass spectrometry and multidimensional NMR spectroscopy, and confirmed through total chemical synthesis of the corresponding diastereoisomers. To our knowledge, this represents the first confirmed tetrahydro-β-carboline post-translational modification in a vertebrate peptide, revealing an unexpected level of chemical innovation in amphibian peptide biosynthesis. Computational analyses of electronic structure identified the Tpi residue as the preferred locus for electron transfer, suggesting a potential role in redox chemistry. ABTS radical-cation scavenging assays demonstrated that the antioxidant activity of the tryptolinophyllins was reduced compared with unmodified tryptophyllins, highlighting a nuanced relationship between post-translational chemical diversification and functional output. Together, these findings expand the known repertoire of naturally occurring peptide modifications in vertebrates and underscore the exceptional chemical plasticity of amphibian skin secretions.

PMID:
42336940
Bibliographic data and abstract were imported from PubMed on 24 Jun 2026.

Read full publication at:
Please sign in to see all details.

Stats

1-terrible, 9-excellent. How would you rate this publication? Sign in in to submit your rating.

Post a comment

You need to be signed in to post comments. You can sign in here.

Comments

There are no comments yet.