High Quality Content by WIKIPEDIA articles! Trypsin is secreted into the duodenum, where it acts to hydrolyse peptides into their smaller building blocks, namely amino acids (these peptides are the result of the enzyme pepsin breaking down the proteins in the stomach). This is necessary for the uptake of protein in the food as though peptides are smaller than proteins, they are still too big to be absorbed through the lining of the ileum. Trypsin catalyses the hydrolysis of peptide bonds.