Question

Below is a metabolic pathway having 3 chemical reactions and 3 enzymes. Enzyme 1 has 2 binding sites--1 for the substrate A and another for the end product D. As the pathway proceeds, the end product in higher quantities will react with enzyme 1, blocking the enzyme's binding to the substrate. Which statement is true about this pathway?
enz1 enz2 enz3
Substrate A --> B --> C --> D end product

Answer 1

Answer:

All options are true. This is an example of  end-product inhibition  which involved non- competitive inhibition.

Explanation:

As more and more products are formed, the product binds binds with the active sites. Therefore preventing the binding of the substrate to form enzyme-substrate complex at the active site. The end products thus acts as an inhibitor disrupting the hydrogen bonding and hydrophobic  interactions of the 3-D structure of protein which holds the active sites. therefore Enzyme active sites losses it specificity, and therefore unable to undergo further catalysis.

Because the end- product of the reaction block the activities of enzyme at   the active sites, it is an inhibitor, therefore the process is known  as End-product inhibition.

Because it is the only substance that  inhibits  with no other product to compete with, it is an example of non-competitive inhibition.

All the options are correct.

Answer 2

Answer:

All statements are true about this pathway.

Explanation:

This is the case of noncompetitive inhibition. In this type of inhibition, the inhibitor reduces or lowers the activity of the enzyme and binds equally well to the enzyme.

So as a result of noncompetitive inhibition, the enzyme will be inhibited and less substrate will be transformed into the end product which is D in this case and eventually this pathway will shut down.  

Also enzyme 1 has 2 binding sites, 1 for the substrate A and another for the end product D.

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