The key difference between substrate and active site is that the substrate is a chemical compound that can undergo a chemical reaction whereas the active site is a specific region on an enzyme.
Enzymes are biological catalysts. These are proteins that can decrease the activation energy of a chemical reaction in order to reduce the energy barrier of that reaction. Hence, it can increase the rate of a reaction. The reactant of the reaction in which enzymes involve is the “substrate”. This substrate binds with the active site of the enzyme. The reactions take place there. Eventually, it releases the products of the reaction.
CONTENTS
1. Overview and Key Difference
2. What is Substrate
3. What is Active Site
4. Side by Side Comparison – Substrate vs Active Site in Tabular Form
5. Summary
What is Substrate?
The substrate is the reactant of a reaction that undergoes a chemical alteration to give products of the reaction. We observe the changes of this compound in order to determine the reaction rate. The enzymes act on this compound in catalytic reactions. When there is a single substrate molecule, it binds with the enzyme, on to the active site of the enzyme. After that, an enzyme-substrate complex forms. Then it undergoes the chemical reaction. Eventually, it converts into the products. These products then release from the active site. But if there are more than one substrate, they will bind with the active site in a particular order. Then they will react together to give the end products.
Figure 01: Reactions to Enzymes
If the substrate gives colored products at the end, then we say the substrate is “chromogenic”. Similarly, if it gives rise to a fluorescent product, we say it is “fluorogenic”. Although enzymes, most of the times, are substrate specific, some enzymes can react with a wide range of substrates.
What is Active Site?
The active site of an enzyme is the region where a substrate binds with the enzyme before it undergoes a chemical reaction. This region has two important sites; binding site and catalytic site. The binding site has residues to which the reactants can temporarily bind. Moreover, it has residues that can catalyze the chemical reaction. Therefore, it is the catalytic site. Furthermore, this region of the enzyme is very small compared to the whole volume of the enzyme. Usually, the active site is consisting of three to four amino acids.
Figure 02: Active Site of an Enzyme
Active sites are specific to substrates. It means each active site has a specific shape which fits a particular substrate. The arrangement of the amino acids in this region determines this specificity. Sometimes, enzymes bind with some cofactors as an aid for their catalytic function. The products of the chemical reaction come out from active sites.
What is the Difference between Substrate and Active Site?
A substrate is the reactant of a reaction that undergoes a chemical alteration to give products of the reaction. This compound gets converted into products. Moreover, it is a chemical compound which acts as the reactant of a chemical reaction. The active site of an enzyme is the region where a substrate binds with the enzyme before it undergoes a chemical reaction. This region converts substrates into products at a lower reaction rate. More importantly, it is a region that is consists of three to four amino acids where a chemical reaction can take place.
Summary – Substrate vs Active Site
Substrate and active site are two terms that we use regarding catalytic reactions that involve enzymes as the catalyst. The difference between substrate and active site is that the substrate is a chemical compound that can undergo a chemical reaction whereas the active site is a specific region on an enzyme.
Reference:
1. “Substrate (Chemistry).” Wikipedia, Wikimedia Foundation, 10 July 2018. Available here
2. “Active Site.” Wikipedia, Wikimedia Foundation, 10 July 2018. Available here
Image Courtesy:
1.’Enzyme-substrate binding’By ImranKhan1992 – Own work, (CC0) via Commons Wikimedia
2.’Enzyme structure’By Thomas Shafee – Own work, (CC BY 4.0) via Commons Wikimedia