VPP 322: Aquatic Animal Diseases, Health Care and Management (1+1)

DIGESTION OF PROTEIN, CARBOHYDRATE AND FAT

Digestion of proteins by the digestive system

• The fishes which possess stomach are generally carnivorous and secrete pepsin enzymes from gastric mucosa. The pepsin is a protease enzyme, i.e., it can break down protein. The trypsin enzymes is produced in th intestine, pancreas and intestinal caecae. The inactive form of this enzymes trypsinogen is known as zymogen. it is also converted into active enzyme, i.e., trypsin by an enzyme enterokinase. The enterokinase enzymes is exclusively secreted by intestine of fish. In  cyprinids, stomachless fish, protease compensation is supplemented by some intestinal enzyme known collectively as trypsin. Pepsin is absent in the stomachless fishes because of the absence of true stomach. The intestine secretes aminopepetidases. These act on terminal amino acid called as exopeptidase and those act on central bonds are called as endopeptidases.

Digestion of carbohydrates

• The enzymes which break down the carbohydrates in the gut of fishes and carbohydrates. They are as follows:
  • Amylase
  • Lactase
  • Saccharases/sucrose
  • Cellulase
• The most important enzyme is amylase which acts on starch and which breakdown to maltose and then to glucose by the process of digestion.

• In those fishes, in which sucrose has been reported the effect is as following

Fat digestion

• The main enzyme which acts on lipid is lipase. The pancreas is  the primary site of lipase production.