The role of lysosomal cysteine proteases in crustacean immune response

Over the long course of evolution and under the selective pressure exerted by pathogens and parasites, animals have selectively fixed a number of defense mechanisms against the constant attack of intruders. The immune response represents a key component to optimize the biological fitness of individuals. Two decades ago, prevention and control of diseases in crustacean aquaculture systems were considered priorities in most shrimp-producing countries, but knowledge was scarce and various pathogens have severely affected aquaculture development around the world. Scientific contributions have improved our understanding of the crustacean immune response. Several studies confirm the central role played by proteases in the immune response of animals, and the cooperative interaction of these enzymes in a wide variety of organisms is well known. This review summarizes the current information regarding the role of cysteine proteases in the immune system of Crustacea and points to aspects that are needed to provide a better integration of our knowledge

Related antipodes: a comparative study on digestive endopeptidases from Northern krill and Antarctic krill (Euphausiacea)

The Antarctic krill, Euphausia superba, and the Northern krill, Meganyctiphanes norvegica, are closely related species but occupy significantly different trophic and climatic environments. E. superba holds a key position as a phytoplankton grazer in the Southern Ocean. The omnivorous M. norvegica is an important member of plankton communities in the Northeast Atlantic. Both species expressed high proteolytic activities which were dominated by serine proteinases. In the stomachs of Antarctic krill, activities of total proteinase, trypsin, and chymotrypsin were significantly higher than in Northern krill. In the midgut glands, however, total proteinase and trypsin activities were similar in both species, but chymotrypsin activity was significantly higher in Antarctic krill. Moreover, Antarctic krill expressed four trypsin isoforms while only one isoform appeared in Northern krill. Chymotrypsin was present in either species as one single isoform. Antarctic krill adapted to the low and patchy distribution of food by elevated enzyme activities and the expression of trypsin isoforms with slightly different catalytic properties. Presumably, these enzymes facilitate in concerted action the efficient utilization of proteins from phytoplankton, the major food. Northern krill, in contrast, seems not to be equipped to face food limitation. It expresses a “simple” or “basic” set of digestive enzymes for utilizing abundant and easily digestible prey