Identification of the Atlantic cod l-amino acid oxidase and its alterations following bacterial exposure

• Atlantic cod Gadus morhua has l-amino acid oxidase (LAO).
• The LAO exists both on body surface and in internal organs.
• The LAO gene is induced upon pathogenic bacterial infection.

Antibacterial factors that are present in epidermal mucus of fish have a potential role in the first line of host defence to bacterial pathogens. This study reports the identification of l-amino acid oxidase (LAO) in Atlantic cod (GmLao) and the changes in the molecule following bacterial exposure. The gmlao transcripts and LAO activity were present on both the body surface and in the internal organs of the fish. Relative mRNA level of gmlao increased significantly in the gills, the spleen and the head kidney (up to 8-fold) of fish that were challenged with the pathogen Vibrio anguillarum. The gmlao expression in skin was 4-fold higher in challenged fish. Our data indicate that LAO may be an important effector of antibacterial defence in Atlantic cod.