Antimicrobial peptides from amphibian skin: an overview

Over the past three decades, numerous peptides have been isolated from amphibian skin secretions. Many of these peptides were shown to be homologous to hormones and neurotransmitters of mammals. In recent years it has been shown that these secretions also contain a multitude of antimicrobial peptides. Most of these peptides are positively charged and have a propensity for forming an amphipathic helix. Other types of peptides have been detected as well, including one group which contain D-allo-isoleucine in their sequences. This work has mainly been done with three species from different families, Xenopus laevis, Bombina variegata and Rana esculenta. Each of these frogs produces distinct sets of peptides which are not related to those of other species. It can therefore be expected that many additional peptides with antimicrobial activity are present in amphibian species from other families.