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What is the difference between trypsin and pepsin?

Posted July 22, 2020


Answer

Although both trypsin and pepsin are proteolytic enzymes secreted by the digestive system in order to digest proteins, they differ in many aspects.

  • Origin: Pepsin is the chief digestive enzyme in stomach, which is produced by the gastric gland in stomach and is a component of gastric juice, while trypsin in produced by the pancreas and is a component of pancreatic juice.
  • Activation: The inactive form of pepsin, pepsinogen, is activated by HCl of the gastric juice, whilst the inactive form of trypsin, trypsinogen, is activated by an enzyme called enterokinase.
  • Catalysis mechanism: Pepsin is an aspartic protease which uses a catalytic aspartate in its active site, while trypsin is a serine protease employing the serine residue in active site.
  • Optimal pH: The optimum pH for pepsin activity is 1.8, while trypsin works best in alkaline pH (pH 7.5-8).
  • Types: Pepsin has four different types, i.e. pepsin A, B, C and D, while trypsin has two types, ?- and ?-trypsin.
  • Specificity: Pepsin hydrolyzes peptide bonds between large hydrophobic amino acid residues, whereas trypsin hydrolyzes peptide bonds at the C-terminal side of lysine or arginine.
  • Function: Pepsin acts on proteins and converts them into peptones, while trypsin converts peptones into polypeptides.
Additional resources

Amplite™ Universal Fluorimetric Protease Activity Assay Kit *Green Fluorescence*

Amplite™ Fluorimetric Proteasome 20S Activity Assay Kit *Green Fluorescence*

Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Scott, M. P., Bretscher, A., ... & Matsudaira, P. (2008). Molecular cell biology. Macmillan.

Berg, J. M., Tymoczko, J. L., & Stryer, L. (2008). Biochemistry (Loose-Leaf). Macmillan.