Difference Between Pepsin and Trypsin

The main difference between pepsin and trypsin is that the pepsin is secreted by the gastric glands of the stomach whereas the trypsin is secreted by the exocrine glands of the pancreas. Furthermore, pepsin functions in an acidic medium while trypsin functions in an alkaline medium. 

Pepsin and trypsin are two types of proteolytic enzymes secreted by the digestive system in order to digest proteins. 

Key Areas Covered 

1. What is Pepsin
     – Definition, Facts, Types
2. What is Trypsin
     – Definition, Facts, Types
3. What are the Similarities Between Pepsin and Trypsin
     – Outline of Common Features
4. What is the Difference Between Pepsin and Trypsin
     – Comparison of Key Differences

Key Terms 

Activation, Applications, Proteolytic Enzymes, Pepsin, Trypsin

What is Pepsin 

Pepsin is the main proteolytic enzyme in vertebrates, which is found in the gastric juice. The inactive precursor of pepsin is pepsinogen produced by the gastric mucosa. Pepsin shows a broad specificity for the peptide linkages in the aromatic or carboxylic L-amino acids. The hydrolysis of the peptide linkages mainly occurs at the C-terminal of the phenylalanine and leucine residues.  

Figure 1: Pepsin A

The four types of pepsin proteins are pepsin A, B (parapepsin I), C (gastricsin), and D (the unphosphorylated form of pepsin A). Pepsin A is the predominant form of gastric protease. Activation of pepsinogen into pepsin requires the protonation of one of the two aspartate residues of the catalytic site. It occurs at the pH between 1-5. 

What is Trypsin 

Trypsin is a pancreatic serine protease with a substrate specificity for positively charged lysine and arginine side chains. The inactive proenzyme of trypsin is trypsinogen produced in the pancreas. The activation of trypsinogen requires the removal of terminal hexapeptide. The two main types of trypsin enzymes are α- and β-trypsin. The predominant form is the α-trypsin.  

Figure 2: Bovine Trypsin

Trypsin is used in tissue dissociation along with the collagenase and elastinase, cell harvesting by trypsinization, etc. 

Similarities Between Pepsin and Trypsin 

• Pepsin and trypsin are two types of digestive enzymes secreted by the digestive system. 
• Both are secreted in the inactive form as zymogens.  
• They are involved in the digestion of proteins by hydrolyzing the peptide bonds. 
• They are collectively called proteases.  

Difference Between Pepsin and Trypsin 

Definition 

Pepsin refers to the chief digestive enzyme in the stomach, which breaks down proteins into polypeptides while trypsin refers to a digestive enzyme which breaks down proteins in the small intestine, secreted by the pancreas as trypsinogen.  

Produced by 

Pepsin is produced by the gastric glands while trypsin is produced by the pancreas.  

Component of 

Also, Pepsin is a component of gastric juice while trypsin is a component of pancreatic juice. 

Types 

The four types of pepsin enzymes are pepsin A, B, C, and D while the two types of trypsin enzymes are α- and β-trypsin.

Secreted into 

Furthermore, the Pepsin is secreted into the stomach while the trypsin is secreted into the duodenum of the small intestine. 

Inactive Form 

The inactive form of the pepsin is pepsinogen while the inactive form of the trypsin is trypsinogen. 

Activation 

Moreover, the inactive form of pepsin is activated by HCl of the gastric juice while the inactive form of trypsin is activated by an enzyme called enteropeptidase.  

Active Site Residues 

Also, the active site residue of pepsin is aspartic acid while the active site residue of trypsin is aspartic acid, histidine, and serine. 

Functions in 

More to this, the Pepsin functions in an acidic medium while trypsin functions in an alkaline medium. 

Enzymatic Action 

Pepsin hydrolyzes peptide bonds between large hydrophobic amino acid residues while trypsin hydrolyzes peptide bonds at the C-terminal side of lysine or arginine.  

Role 

Pepsin is responsible for converting proteins into proteoses and peptones while trypsin is responsible for converting proteins into polypeptides. 

Inhibitors 

Inhibitors of pepsin are aliphatic alcohols, pepsin A, and substrate-like epoxidase while the inhibitors of trypsin are DFP, aprotinin, Ag⁺, EDTA, benzamidine, etc. 

Applications 

Pepsin is used in the digestion of antibodies, preparation of collagen, protein digestibility assays, and subculturing viable mammary epithelial cells while trypsin is used in tissue dissociation, cell harvesting, mitochondrial isolation, in vitro protein studies, etc. 

Conclusion 

The Pepsin is the major type of proteolytic enzyme in vertebrates found in the gastric juice while the trypsin is the proteolytic enzyme found in the pancreatic juice. The main difference between pepsin and trypsin is their properties and function.   

Reference:

1. “Pepsin.” Catalase – Worthington Enzyme Manual, Available Here
2. “Trypsin.” Catalase – Worthington Enzyme Manual, Available Here

Image Courtesy:

1. “1PSO” By No machine-readable author provided. DrKjaergaard assumed (based on copyright claims). – No machine-readable source provided. Own work assumed (based on copyright claims). (Public Domain) via Commons Wikimedia 
2. “1UTN” By user:DrKjaergaard – Own work: From PDB file 1UTN. Created with PyMol. (Public Domain) via Commons Wikimedia