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Difference Between Feedback Inhibition and Feedback Repression

The key difference between feedback inhibition and feedback repression is that in feedback inhibition, the product inhibits the enzyme by binding with the active site of the enzyme and prevents the formation of the substrate-enzyme complex. Meanwhile, in feedback repression, end product inhibits the enzyme by inhibiting the production of the enzyme at the gene level.
Enzymes participate in biochemical reactions. They act as biocatalysts and speed up the reactions. Also, they can be inhibited in different ways. Feedback inhibition and feedback repression are two ways of enzyme inhibition. In feedback inhibition, the product itself inhibits the enzyme in order to control the amount of product. The product binds with the active site of the enzyme and prevents the binding of the substrate with the enzyme. In feedback repression, the end product inhibits the production of the enzyme at the gene level.

What is Feedback Inhibition?

Feedback inhibition is a way of controlling the production of the end product. Generally, biochemical reactions occur as a series of reactions. In feedback inhibition, the final product inhibits the first enzyme known as the allosteric enzyme, which catalyzes the first reaction. It does it by binding with the active site of the enzyme. Once the end product binds with the enzyme, it prevents the binding of the substrate with the enzyme. In this way, the activity of the enzyme is blocked or inhibited. As a result, the biochemical pathway is shut down, and the amount of end product is controlled. Feedback inhibition occurs in many biochemical pathways of all living organisms.

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The feedback inhibition can be relieved by using the end product. Then the end product will not inhibit the enzyme. By doing it, the organism can resume the biochemical pathway and synthesis of the end product.

What is Feedback Repression?

Feedback repression is another way of enzyme inhibition. In feedback repression, the accumulated end products repress the synthesis of the very first enzyme that catalyzes the initial stage of the biochemical pathway. It occurs at the gene or genetic level.  When the product formation exceeds the optimal amount, the product itself inhibits the production by inhibiting the synthesis of the enzyme in feedback repression. The end products work as repressors and bind with DNA of the gene that code for the enzyme and prevent the synthesis of the enzyme.

What are the Similarities Between Feedback Inhibition and Feedback Repression?

1.Feedback inhibition and feedback repression are two types of enzyme inhibition mechanisms.
2.In both methods, the accumulated end products work for the inhibition of the enzyme.
3.These methods control the production of end products of the biochemical pathways.

What is the Difference Between Feedback Inhibition and Feedback Repression?

Feedback inhibition is the mechanism in which the accumulated end product binds with the enzyme and inhibits the enzyme activity by binding with it. On the other hand, feedback repression is the mechanism in which the accumulated end product works as a repressor and inhibits the enzyme synthesis at the genetic level. So, this is the key difference between feedback inhibition and feedback repression.

Moreover, end product binds with the active site of the enzyme in feedback inhibition while end product binds with the DNA of the gene that encodes the enzyme and prevents the synthesis of the enzyme. Therefore, this is also a difference between feedback inhibition and feedback repression.

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Summary – Feedback Inhibition vs Feedback Repression

Feedback inhibition refers to the inhibition of enzymes by the end product of the biochemical pathway due to binding with the regulatory site of the enzyme and preventing the binding of the substrate to the enzyme. In simple words, the inhibition of an enzyme by its product is called feedback inhibition. Feedback repression refers to the inhibition of the enzyme by the end product or its derivatives by inhibiting the production of the enzyme at the genetic level. So, this is the key difference between feedback inhibition and feedback repression.

Reference:

1. Todar, Kenneth, and Madison. Regulation of Bacterial Metabolism, Available here.
2. Koshland, Daniel E., and Felix Haurowitz. “Inhibition of Enzymes.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 26 Dec. 2019, Available here.

Image Courtesy:

1. “Feedback Inhibition in Glycolysis (MMG 301 Honors Option)” By Phill729 – Own work (CC BY-SA 4.0) via Commons Wikimedia