Identification and Characterization of a Novel Gene-encoded Antioxidant Peptide from Odorous Frog Skin

Amphibian skin plays an essential role in protecting organisms from harmful external factors such as UV radiation. How amphibians protect themselves from reactive oxygen species following long-term sun exposure is an important and interesting question. Amphibian skins possess a novel antioxidant system composed of various Antioxidant Peptides (AOPs), which maintain redox homeostasis. However, only a few AOPs have been identified so far.

Using combinational methods of peptidomics and genomics, we characterized a novel gene-encoded antioxidant peptide (herein named OA-VI12) from Odorrana andersonii skin secretions, which was produced by the post-translational processing of a 59-residue prepropeptide. The amino acid sequence of the OA-V112 was 'VIPFLACRPLGL', with a molecular mass of 1298.6 Da and no observed post-transcriptional modifications. Functional analysis demonstrated that OA-VI12 was capable of scavenging ABTS+, DPPH, NO and decreasing the Fe3+ production.

We determined that the C7 amino acid was responsible for ABTS+ and Fe3+ scavenging, activities, the F4, C7, and P9 amino acids were crucial for DPPH scavenging activity, and the P9 amino acid was responsible for NO scavenging activity. Unlike several other amphibian peptides, OA-VI12 did not accelerate wound healing in a full-thickness skin-wound mouse model and did not demonstrate direct microbial killing. Here, we identified and named a novel gene-encoded antioxidant peptide from the skin secretions of an odorous frog species, which may assist in the development of potential antioxidant candidates.

This study may help improve our understanding of the molecular basis of amphibians' adaptation to environments experiencing long-term UV radiation.