Identification of an antibacterial protein as L-amino acid oxidase in the skin mucus of rockfish Sebastes schlegeli.

摘要: Fish skin mucus contains a variety of antimicrobial proteins and peptides that seem to play role in self defense. We previously reported an antibacterial protein the secretion rockfish, Sebastes schlegeli, which showed selective activity against Gram-negative bacteria. This study aimed isolate structurally functionally characterize this protein. The protein, termed SSAP (S. schlegeli protein), was purified homogeneity by lectin affinity column chromatography, anion-exchange HPLC hydroxyapatite HPLC. It found be glycoprotein containing N-linked glycochains FAD. Its molecular mass estimated 120 kDa gel filtration 53 kDa SDS/PAGE, suggesting it is homodimer. On basis partial amino-acid sequence determined, full-length cDNA 2037 bp including ORF 1662 bp encodes 554 residues cloned 3′ RACE, 5′ RACE RT-PCR. A blast search mature (496 residues) homologous l-amino acid oxidase (LAO) family proteins. determined have LAO H2O2-generation assay substrate specificity for only l-Lys with Km 0.19 mm. potent fish pathogens such as Aeromonas hydrophila, Aeromonas salmonicida Photobacterium damselae ssp. piscicida. completely lost on addition catalase, confirming H2O2 responsible growth inhibition. identifies new member reveals involvement innate immunity skin.