In the equation below, substrate C is an allosteric...

In the equation below, substrate $C$ is an allosteric inhibitor to enzyme 1. Which of the following is another mechanism necessarily caused by substrate $C ?$ $$\mathrm{A} \underset{\text { enzyme } 1}{\longrightarrow} \mathrm{B} \underset{\text { enzyme } 2}{\longrightarrow} \mathrm{C}$$ (A) Competitive inhibition (B) Irreversible inhibition (C) Feedback enhancement (D) Negative feedback

In the equation below, substrate $C$ is an allosteric inhibitor to enzyme 1. Which of the following is another mechanism necessarily caused by substrate $C ?$
$$\mathrm{A} \underset{\text { enzyme } 1}{\longrightarrow} \mathrm{B} \underset{\text { enzyme } 2}{\longrightarrow} \mathrm{C}$$
(A) Competitive inhibition
(B) Irreversible inhibition
(C) Feedback enhancement
(D) Negative feedback

Key Concepts

Feedback Inhibition

Feedback inhibition is a regulatory mechanism in which the end product of a metabolic pathway inhibits an enzyme that acts early in the pathway. This negative feedback loop helps maintain homeostasis by preventing the accumulation of the end product and conserving cellular resources.

Allosteric Regulation

This concept involves the modulation of an enzyme’s activity through the binding of an effector molecule at a site other than the enzyme’s active site. The binding can result in either an increase or decrease in enzyme activity, influencing the overall reaction rate and allowing fine-tuned control over metabolic pathways.

Transcript

00:01 This question asks, in the equation below, substrate c is an allosteric inhibitor to enzyme 1, which of the following is another mechanism necessarily caused by substrate c.

00:11 So we have a proceeding to b and b proceeding to c in the presence of enzyme 1 and enzyme 2.

00:21 Now we know that substrate c is going to be an inhibitor to enzyme 1.

00:29 So it will actually inhibit enzyme 1.

00:32 So what kind of inhibition or feedback would this be? well, if we are using a downstream product to inhibit an upstream enzyme or catalyst, then we are performing negative feedback.

00:53 So allosteric inhibition will rule out the fact that it is competitive inhibition.

00:58 Because alasdic inhibition, if we take a look at our enzyme, let's say this is our enzyme right here, and it will have its active site right there, but it will also have a separate site known as the allosteric site, which will allow for allosteric binding of different substrates that will have an effect on enzymatic activity.

01:29 So usually if we have binding at the allosteric site, perhaps there will be a conformational change that will cause that active site to disappear or be functionally inactivated.

01:40 So this would not be competitive inhibition since we're talking about an allosteric inhibitor and not a competitive inhibitor.

01:47 So that's why a choice a is going to be eliminated.

01:51 This is not necessarily irreversible because if we just eliminate choice, if we eliminate substrate c, then there will be no more inhibition of enzyme one.

01:58 So it will go back to its normal activity.

02:02 So that's why choice b is removed.

02:04 And then this is not enhancement, right? because what happens in this situation? well, substrate c is going to knock out enzyme one.

02:13 So it means that this reaction from a to b will proceed much, much, much, much slower, perhaps to the point where it won't proceed at all.

02:23 So that means that from b to c, well, if we're going to have a reduction in b, we're going to have a drastic reduction in c.

02:31 Or we won't be able to produce as much.

02:33 So basically this reaction will be canceled out...

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