Chymotrypsin vs. Trypsin

Attribute	Chymotrypsin	Trypsin
Enzyme Type	Serine protease	Serine protease
Substrate Specificity	Hydrolyzes peptide bonds after aromatic amino acids (Phe, Trp, Tyr)	Hydrolyzes peptide bonds after basic amino acids (Lys, Arg)
Optimal pH	pH 7-9	pH 7-9
Optimal Temperature	37°C	37°C
Activation	Activated by trypsin	Activated by enterokinase
Location	Found in the pancreas	Found in the pancreas and small intestine

Introduction

Proteases are enzymes that play a crucial role in the breakdown of proteins into smaller peptides or amino acids. Chymotrypsin and trypsin are two well-known serine proteases that are involved in the digestive process. While both enzymes share similarities in their structure and function, they also exhibit distinct attributes that make them unique. In this article, we will explore and compare the attributes of chymotrypsin and trypsin, shedding light on their similarities and differences.

Structure

Chymotrypsin and trypsin belong to the same family of serine proteases and share a similar overall structure. They both consist of a single polypeptide chain folded into two domains: an N-terminal domain and a C-terminal domain. The active site of both enzymes is located in a cleft between these two domains. However, there are notable differences in the specific arrangement of amino acids within their active sites, which contribute to their divergent substrate specificities.

Substrate Specificity

One of the key differences between chymotrypsin and trypsin lies in their substrate specificities. Chymotrypsin primarily cleaves peptide bonds adjacent to large hydrophobic amino acids, such as phenylalanine, tryptophan, and tyrosine. This specificity allows chymotrypsin to target proteins with bulky hydrophobic side chains. On the other hand, trypsin specifically cleaves peptide bonds adjacent to positively charged amino acids, such as lysine and arginine. This preference for basic amino acids makes trypsin particularly effective in digesting proteins rich in these residues.

Activation

Both chymotrypsin and trypsin are initially synthesized as inactive zymogens, namely chymotrypsinogen and trypsinogen, respectively. Activation of these enzymes is crucial to prevent premature proteolysis within the cells where they are produced. Chymotrypsinogen is activated by the proteolytic cleavage of a specific peptide bond, resulting in the formation of two chains held together by disulfide bonds. In contrast, trypsinogen is activated by the cleavage of a different peptide bond, leading to the removal of an inhibitory peptide and the subsequent rearrangement of the remaining chains. Once activated, both chymotrypsin and trypsin can catalyze the activation of additional zymogen molecules, amplifying their proteolytic activity.

Optimal pH

Another important attribute to consider when comparing chymotrypsin and trypsin is their optimal pH for activity. Chymotrypsin exhibits maximum activity in a slightly alkaline environment, with an optimal pH range of 7.5 to 8.0. This pH range is consistent with the conditions found in the small intestine, where chymotrypsin is primarily active. In contrast, trypsin functions optimally in a slightly acidic environment, with an optimal pH range of 7.0 to 8.0. This pH range is more suitable for the conditions in the stomach, where trypsin is predominantly active.

Inhibition

Both chymotrypsin and trypsin can be inhibited by specific inhibitors to regulate their activity. One common inhibitor for both enzymes is aprotinin, a small protein derived from bovine lung tissue. Aprotinin binds to the active site of chymotrypsin and trypsin, preventing substrate binding and subsequent proteolysis. Additionally, chymotrypsin can be inhibited by serpins, a family of serine protease inhibitors, which form a covalent complex with the active site of the enzyme. In contrast, trypsin can be inhibited by pancreatic trypsin inhibitor (PTI), a small protein that binds to the active site of trypsin, blocking its activity.

Physiological Functions

Chymotrypsin and trypsin play distinct roles in the digestive process. Chymotrypsin is primarily responsible for the hydrolysis of peptide bonds in proteins, breaking them down into smaller peptides. It acts in synergy with other pancreatic enzymes, such as elastase and carboxypeptidase, to ensure efficient protein digestion. On the other hand, trypsin is involved in the activation of other pancreatic zymogens, including chymotrypsinogen and procarboxypeptidase, by cleaving specific peptide bonds. This activation cascade ensures the sequential release of active enzymes required for complete protein digestion.

Conclusion

In conclusion, chymotrypsin and trypsin are two serine proteases that share similarities in their structure and function, yet exhibit distinct attributes that make them unique. While both enzymes possess similar overall structures and are involved in protein digestion, they differ in their substrate specificities, optimal pH ranges, and physiological functions. Understanding the attributes of chymotrypsin and trypsin provides valuable insights into their roles in the digestive process and their potential applications in various fields, including biotechnology and medicine.