Answer :
In the case of a feedback-regulated enzymatic pathway, the statement that is most likely to be true is that the end product of the pathway inhibits the activity of the first enzyme in the pathway. This is known as feedback inhibition.
Feedback inhibition is a regulatory mechanism in which the end product of a metabolic pathway inhibits the activity of an earlier enzyme in the pathway.
This allows the cell to regulate the production of the end product based on its current needs.
Here's a step-by-step explanation of how feedback inhibition works in a feedback-regulated enzymatic pathway:
1. The pathway begins with the first enzyme, which catalyzes the initial step of the pathway.
2. As the pathway progresses, intermediate molecules are converted into the end product.
3. When the concentration of the end product reaches a certain level, it binds to a specific site on the first enzyme, causing a conformational change in the enzyme.
4. This conformational change inhibits the activity of the first enzyme, preventing further production of the end product.
5. As a result, the concentration of the end product decreases, and the inhibition is relieved.
6. When the concentration of the end product decreases below a certain threshold, the first enzyme regains its active conformation, and the pathway resumes.
An example of feedback inhibition can be seen in the regulation of the production of the amino acid isoleucine.
The pathway for isoleucine synthesis involves several enzymes, with the last step being catalyzed by the enzyme threonine deaminase.
The end product, isoleucine, binds to threonine deaminase and inhibits its activity when the concentration of isoleucine is high.
This prevents overproduction of isoleucine.
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