Difference Between Trypsin and Chymotrypsin

The main difference between trypsin and chymotrypsin is that the trypsin cleaves at the C-terminal arginine and lysine residues whereas the chymotrypsin cleaves at the C-terminal phenylalanine, tryptophan, and tyrosine residues. This means trypsin acts upon basic amino acids while chymotrypsin acts upon aromatic amino acids. 

Trypsin and chymotrypsin are two types of protein-digestive enzymes that cleave peptide bonds at the C-terminal. They are secreted by the exocrine glands of the pancreas in their inactive forms called zymogens. 

Key Areas Covered 

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

Key Terms 

Chymotrypsin, Chymotrypsinogen, Pancreas, Proteolytic Enzymes, Trypsin, Trypsinogen

What is Trypsin 

Trypsin is a serine protease with a substrate specificity towards the basic amino acids such as lysine and arginine. It is produced by the pancreas and is secreted in its inactive form called trypsinogen. The activation of trypsinogen is by the removal of the terminal hexapeptide with the action of enterokinase. The two main types of trypsin are α- and β-trypsin. 

Figure 1: Trypsin Mechanism of Action

Trypsin is an important enzyme used for other purposes apart from its function in the digestive system. It is used in tissue dissociation and cell harvesting from cultures as well.  

What is Chymotrypsin 

Chymotrypsin is a serine endopeptidase with a substrate specificity towards the phenylalanine, tryptophan, and tyrosine side chains, which are mainly large hydrophobic residues. It is produced by acinar cells of the pancreas and secreted in its inactive form called chymotrypsinogen. The activation of chymotrypsinogen is basically by the enzymatic action of trypsin. The two main types of chymotrypsin are chymotrypsin A and B.  

Figure 2: Chymotrypsin Active Site

The structure of the trypsin and chymotrypsin is similar except the S1 site of chymotrypsin, which gives the substrate-specific catalysis of chymotrypsin.  

Similarities Between Trypsin and Chymotrypsin 

• Trypsin and chymotrypsin are proteolytic enzymes secreted by the pancreas. 
• They are released to the small intestine at the duodenum. 
• Both are secreted in their inactive forms. The active site residues of both trypsin and chymotrypsin are histidine, aspartate, and serine. 
• They aid in the enzymatic digestion of proteins. 
• Low amounts of trypsin and chymotrypsin in stool are indicators of cystic fibrosis and pancreatic disease such as pancreatitis. 

Difference Between Trypsin and Chymotrypsin 

Definition 

Trypsin refers to a digestive enzyme that breaks down proteins in the small intestine, secreted by the pancreas as trypsinogen while chymotrypsin refers to a digestive enzyme secreted by the pancreas and converted into the active form by trypsin. 

Types 

The α- and β-trypsin are the two types of trypsin while chymotrypsin A and B are the two types of chymotrypsin. 

Inactive Form  

Also, the inactive form of trypsin is trypsinogen while the inactive form of chymotrypsin is chymotrypsinogen. 

Activation 

Furthermore, trypsinogen is activated by enterokinase while chymotrypsinogen is activated by trypsin.

Enzymatic Action 

Moreover, trypsin hydrolyzes peptide bonds at the C-terminal side of lysine or arginine while chymotrypsin hydrolyzes peptide bonds at the C-terminal side of phenylalanine, tryptophan, and tyrosine. This is one main difference between trypsin and chymotrypsin.

Inhibitors 

In addition, the inhibitors of trypsin are DFP, aprotinin, Ag+, EDTA, benzamidine, etc. while the inhibitors of chymotrypsin are hydroxymethylpyrroles, boronic acids, courmarin derivatives, peptidyl aldehydes, etc. 

Applications 

Considering the applications, trypsin is used in tissue dissociation, cell harvesting, mitochondrial isolation, in vitro protein studies, etc. while chymotrypsin is used in sequence analysis, peptide synthesis, peptide mapping, peptide fingerprinting, etc. 

Conclusion 

Trypsin is the protein-digestive enzyme that cleaves the peptide bonds at the C-terminal basic amino acids such as lysine and arginine. However, chymotrypsin is another protein-digestive enzyme that cleaves peptide bonds at the C-terminal large hydrophobic amino acids such as phenylalanine, tryptophan, and tyrosine. Both trypsin and chymotrypsin are secreted by the pancreas in their inactive form. The main difference between trypsin and chymotrypsin is the type of enzymatic action. 

Reference:

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

Image Courtesy:

1. “BAPNA assay” By Volker Gatterdam – Own work (CC BY-SA 3.0) via Commons Wikimedia 
2. “Chymotrypsin” By Jcwhizz (CC BY-SA 3.0) via Commons Wikimedia