Fish Nutrition & Feed Technology

Unit 3 - Proteins and Amino acids

3.5.Protein Digestion and Metabolism

Ingested proteins are first split into peptides by pepsin in the stomach or by trypsin and chymotrypsin from the pancreas. These peptides are then further reduced by the action of carboxypeptidase which hydrolyzes off one amino acid at a time beginning at the free carboxyl end of the molecule or by amino peptidase which splits off one amino acid at a time beginning at the free amino end of the polypeptide chain. The free amino acids released into the digestive system are then absorbed through the walls of the gastro intestinal tract into the blood stream where they are then re-synthesized into new tissue proteins or are catabolyzed for energy or for fragments for further tissue metabolism.