Skin mucus protease from rainbow trout, Salmo gairdneri Richardson, and its biological significance

The skin mucus of rainbow trout, salmon, charr, cod, coalfish, plaice and redfish contain, besides lysozyme and haemagglutinins, protease activity. The mucus protease from rainbow trout has been purified, characterized and shown to be indistinguishable from the trypsin produced in pylorus caecae. This enzyme activity can escape detection in mucus since it is inhibited by serum components which may contaminate the skin mucus as a result of stress and handling of the fish prior to collecting the mucus.