Food digestion involves digestive enzymes to break down polymeric macromolecules and facilitate nutrient absorption. Enzyme supplementation in aquafeeds is a major alternative to improve feed quality and nutrient digestibility, gut health, compensate digestive enzymes when needed, and may also improve
Cathepsin D alone and in combination with other cathepsins presents the greatest proteolytic activity on some fish muscles.
Cathepsins B, D and L are considered critical in fish muscle post-mortem modifications or gel softening during the setting of surimi.
Protease enzymes are important industrial enzymes that have diverse applications in food, leather, silk and the agrichemical and pharmaceutical industries. Fish are considered one of the richest sources of proteolytic enzymes.
Digestive enzymes in fish can cause post-harvest tissue degradation, an effect that is most pronounced when connective tissue is affected. Some parasites produce enzymes that make seafood appear unsuitable for human consumption.
The most important factors in the loss of quality in seafood are nucleotide catabolism and glycolysis. The rates and pathways of nucleotide degradation vary with species and muscle type.