What is the Difference Between Binding Site and Catalytic Site

The main difference between binding site and catalytic site is that the binding site temporarily binds with the substrate whereas the catalytic site catalyzes the reaction of the substrate.

The binding site and catalytic site are two components of the active site of an enzyme. Generally, enzymes are polypeptide molecules with a high three-dimensional structural complexity. The main function of enzymes is to catalyze biochemical reactions.

Key Areas Covered

1. What is a Binding Site
   • Definition, Characteristics, Importance
2. What is a Catalytic Site
   • Definition, Characteristics, Importance
3. Similarities Between Binding Site and Catalytic Site
   • Outline of Common Features
4. Difference Between Binding Site and Catalytic Site
   • Comparison of Key Differences

Key Terms

Binding Site, Catalytic Site

What is a Binding Site

The binding site is the location of substrates binding with the enzyme. Generally, it is one of the two components of the active site of the enzyme. More importantly, the active site is the site of the enzyme where the substrate molecules bind and undergo the chemical reaction. The active site of an enzyme contains specific amino acid residues that form temporary bonds with the substrate. Generally, the site where the substrate binds to the enzyme is the binding site. The main function of the binding site is to bind and orient substrate molecules.

Figure 1: Active Site

Furthermore, the active site of the enzyme occupies ~10–20% of the total volume of the enzyme. It is the most important part of the enzyme that catalyzes the chemical reaction. Normally, the active site of the enzyme contains only three to four amino acids. Other amino acids of the enzyme are important in maintaining the tertiary structure of the enzyme.    

What is Catalytic Site

The catalytic site is the location where the catalysis of the chemical reaction occurs in the enzyme. Therefore, the amino acids in the catalytic site of the enzyme are responsible for catalyzing the chemical reaction. The catalytic site reduces the activation energy of the chemical reaction. The catalytic site is one of the two main components of the active site of an enzyme. In general, the main function of an enzyme is to catalyze a chemical reaction under physiological conditions.

Figure 2: Catalytic Site in Red

The most significant feature of the active site of the enzyme along with the binding site and catalytic site is the specificity of the enzyme. Furthermore, the amino acid residues in the active site of the enzyme determine the specificity of the enzyme. Therefore, the binding site of the enzyme binds to specific substrate molecules and the catalytic site of the enzyme undergoes a specific chemical reaction.

Similarities Between Binding Site and Catalytic Site

• The binding site and catalytic site are the two components of the active site of an enzyme.
• Moreover, their main function is to catalyze biochemical reactions.

Difference Between Binding Site and Catalytic Site

Definition

The binding site refers to a location on a macromolecule or cellular structure at which chemical interaction with a specific active substance takes place, while the catalytic site refers to a portion of an enzyme molecule at which the actual reaction proceeds and is considered to consist of one or more residues or atoms in a spatial arrangement.

Significance

The binding site temporarily binds with the substrate while the catalytic site catalyzes the reaction of the substrate.

Function

Moreover, the binding site binds and orients the substrate while the catalytic site reduces the chemical activation energy.

Conclusion

In brief, the binding site and catalytic site are the two components of the active site of an enzyme. However, the main function of an enzyme is to catalyze biochemical reactions. The binding site temporarily binds with the substrate and its function is to bind and orient the substrates. In contrast, the catalytic site catalyzes the biochemical reactions and the main function of the catalytic site is to reduce chemical activation energy. Therefore, the main difference between binding site and catalytic site is their function.

References:

1. “Active Site.” Wikipedia, Wikimedia Foundation, 25 May 2022.

Image Courtesy:

1. “Enzyme structure” By Thomas Shafee – Own work (CC BY 4.0) via Commons Wikimedia
2. “Catalytic triad of TEV protease” By Thomas Shafee- Own Work (CC BY 4.0) via Commons Wikimedia