Structure and function of a novel antioxidant peptide from the skin of tropical frogs

Publication date: 1 February 2018
Source:Free Radical Biology and Medicine, Volume 115
Author(s): Eder Alves Barbosa, Ana Oliveira, Alexandra Plácido, Renato Socodato, Camila C. Portugal, Ana Carolina Mafud, Alicia S. Ombredane, Daniel C. Moreira, Nuno Vale, Lucinda J. Bessa, Graziella A. Joanitti, Cláudia Alves, Paula Gomes, Cristina Delerue-Matos, Yvonne Primerano Mascarenhas, Mariela M. Marani, João B. Relvas, Manuela Pintado, José Roberto S.A. Leite
The amphibian skin plays an important role protecting the organism from external harmful factors such as microorganisms or UV radiation. Based on biorational strategies, many studies have investigated the cutaneous secretion of anurans as a source of bioactive molecules. By a peptidomic approach, a novel antioxidant peptide (AOP) with in vitro free radical scavenging ability was isolated from Physalaemus nattereri. The AOP, named antioxidin-I, has a molecular weight [M+H]⁺ = 1543.69Da and a TWYFITPYIPDK primary amino acid sequence. The gene encoding the antioxidin-I precursor was expressed in the skin tissue of three other Tropical frog species: Phyllomedusa tarsius, P. distincta and Pithecopus rohdei. cDNA sequencing revealed highly homologous regions (signal peptide and acidic region). Mature antioxidin-I has a novel primary sequence with low similarity compared with previously described amphibian's AOPs. Antioxidin-I adopts a random structure even at high concentrations of hydrophobic solvent, it has poor antimicrobial activity and poor performance in free radical scavenging assays in vitro, with the exception of the ORAC assay. However, antioxidin-I presented a low cytotoxicity and suppressed menadione-induced redox imbalance when tested with fibroblast in culture. In addition, it had the capacity to substantially attenuate the hypoxia-induced production of reactive oxygen species when tested in hypoxia exposed living microglial cells, suggesting a potential neuroprotective role for this peptide.

Graphical abstract

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