Pancreatic juice contains a variety of inactive enzymes such as trypsinogen, chymotrypsinogen, and carboxypeptidases. These enzymes play an important role in the digestion of proteins.

Physiology of protein-digestion

The enzyme enterokinase is secreted by the intestinal mucosa. It activates trypsinogen into trypsin.

$\mathrm{Trypsinogen}\stackrel{\mathrm{Enterokinase}}{\to }\mathrm{Trypsin}+\mathrm{Inactive} \mathrm{peptide}$

Trypsin then activates the other enzymes of pancreatic juice such as chymotrypsinogen
and carboxypeptidase.

Chymotrypsinogen is a milk-coagulating enzyme that converts proteins into peptides.

$\underset{\left(\mathrm{Inactive}\right)}{\mathrm{Chymotorypsinogen}}\stackrel{\mathrm{Trypsin}}{\to }\underset{\left(\mathrm{Active}\right)}{\mathrm{Chymotrypsin}}$

$\mathrm{Proteins}\stackrel{\mathrm{Chymotrypsin}}{\to }\mathrm{Peptides}$

Carboxypeptidase acts on the carboxyl end of the peptide chain and helps release the last amino acids. Hence, it helps in the digestion of proteins.

$\mathrm{Peptides}\stackrel{\mathrm{Carboxypeptidase}}{\to }\mathrm{Smaller} \mathrm{peptide} \mathrm{chain}+\mathrm{Amino} \mathrm{acids}$

Thus, in short, we can say that the partially-hydrolysed proteins present in the chyme are acted upon by various proteolytic enzymes of the pancreatic juice for their complete digestion.

$\mathrm{Proteins}, \mathrm{peptones}\underset{\mathrm{Carboxypeptidase}}{\overset{\mathrm{Trypsin}/\mathrm{Chymotrypsin}}{\to }}\mathrm{Dipeptides} \mathrm{and} \mathrm{proteases}$