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Updated: May 25, 2026

Construction of Cyclic Cell-Penetrating Peptides for Enhanced Penetration of Biological Barriers
Published on: September 19, 2022
Calyxamides A and B, cytotoxic cyclic peptides from the marine sponge Discodermia calyx
Miki Kimura1, Toshiyuki Wakimoto, Yoko Egami
1Graduate School of Pharmaceutical Sciences, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Abstract:
Cyclic peptides containing 5-hydroxytryptophan and thiazole moieties were isolated from the marine sponge Discodermia calyx collected near Shikine-jima Island, Japan. The structures of calyxamides A (1) and B (2), including the absolute configurations of all amino acids, were elucidated by spectroscopic analyses and degradation experiments. The structures are similar to keramamides F and G, previously isolated from Theonella sp. The analysis of the 16S rDNA sequences obtained from the metagenomic DNA of D. calyx revealed the presence of Candidatus Entotheonella sp., an unculturable δ-proteobacterium inhabiting the Theonella genus and implicated in the biosynthesis of bioactive peptides.
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