The acid chyme released from the stomach into the intestinal lumen may contain digested protein (by pepsin) or native protein (untouched by pepsin if any) apart from carbohydrates and fats. The acid chyme is first neutralised by bicarbonates of pancreatic juice and then acted upon by various enzymes. The proteins in the chyme are acted upon by the proteolytic enzymes of the
- Pancreatic juice – namely trypsin, chymotryr.in and carboxypeptidase.
- ‘Intestinal juice – aminopeptidase, tripeptidase and dipeptidases.
Among these trypsin and chymotrypsin are endopeptidases (attacking internal peptide bonds) acting on native protein and the carboxypeptidases, aminopeptidases, tri and dipeptidases are exopeptidases (attacking superficial peptide bonds at the carbxyl end or amino end respectively) acting on protein fragments produced from whole or native proteins.
The action of the above enzymes on proteins is as follows;
(i) Trypsin and Chymotrypsin act on native proteins splitting or reducing them into shorter protein chains namely proteoses, peptones and polypeptides.
proteoses,peptones,polyheptides
(ii) Carboxypeptidases and amino peptidases act on the protein molecules got from the digestion of native proteins converting them into tripeptides, dipeptides and amino acids.
(iii) The tri and dipeptides resulted from the above reactions are acted upon by tri and dipeptidases and split into amino acids.
Finally, resulting in a pool of amino acids which can be easily absorbed.
