Intracellular protein degradation in the development of the atlantic salmon Salmo salar L.

Through the example of the Atlantic salmon Salmo salar L. we provide here the quick details on the universal and specific features of the proteolytic apparatus in the skeletal muscles of fish. Among the numerous muscle tissue proteases, the most comprehensively studied are those which determine the protein degradation levels in the efficiently growing and developing muscles of the salmon juveniles and by this way regulate the protein accumulation rates in muscles and the overall growth processes in the organism, namely, the lysosomal cathepsins B and D and calcium-dependent proteases (calpains). We have detected the age-related differences in the activity of the intracellullar proteases in salmon muscles, which suggest the important role of the proteolysis regulation in growth and the specific role for the certain proteolytic enzymes. For example, we have obtained data indicating the negative correlation between the cathepsin D and calpains activity levels in muscle tissue and the weight gain rate in the salmon of different age groups. The detected positive correlation between the cathepsin B activity and the morphometric indices in juvenile fish is apparently indicative of the key role of this enzyme in the metabolism of proteins of the predominantly nonmyofibrillar nature.