How does an irreversible inhibitor function differently than a reversible inhibitor?

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Accepted Answer

All right. Hello everyone. So this question is asking us which of the following statements differentiates the function of irreversible and reversible inhibitors. So here we have four different answer choices labeled A through D. Now, what's interesting about the answer choices themselves is that they propose a different type of interaction between the inhibitor and the enzyme. In question whether it's intermolecular bonds, covalent bonds, ionic bonds or dile dippo bonds just to name a few, right? So really the question is what is the difference between irreversible and reversible inhibitors in terms of how they, how they interact with the enzyme? And what does that mean for their effect on enzyme kinetics? So let's talk about those differences and let me just scroll down to open up some more space here. So as mentioned before in the question, right, we can differentiate between irreversible and reversible inhibition. So let's start with irreversible inhibition. Well, recall that the reason why this type of inhibition is called irreversible is because oftentimes a covalent bond is formed between the enzyme and the inhibitor itself. So what happens as a result of this? Well, because you have a covalent bond forming, what happens is that you create a stable complex involving both the inhibitor and the enzyme itself. And so, because you have this stable complex, what essentially happens is that the substrate is no longer able to bind to the active side of the enzyme. And this leads therefore to permanent inactivation of that enzyme. So the substrate is no longer able to bind. Now, by contrast, when it comes to reversible inhibition, a reversible inhibitor is going to engage in non covalent interactions with the enzyme itself. And so because the interaction between these two species is not covalent, what happens is that dissociation is possible, right? At some point, the inhibitor can dissociate from the enzyme and allow the enzyme to bind to the substrate once more. Now, within this realm of reversible inhibition, recall that there is three distinct categories because we can talk about competitive reversible inhibition where the inhibitor and the substrate compete for the same binding site. We can also talk about noncompetitive inhibition, noncompetitive reversible inhibition. And we can also talk about uncompetitive inhibition. Now, both noncompetitive and uncompetitive inhibition involve the inhibitor binding to a different site on the enzyme. So not the active site itself. So what happens then as a result of each, what is the effect on enzyme kinetics in the case of each of these types of inhibition? Well, going back to reversible inhibition. What happens as a result of, excuse me, irreversible inhibition is that the number of active enzyme molecules is going to decrease because at this point several have been inactivated. And so therefore, the V max of the reaction, which is the maximal reaction rate is going to decrease. But it's worth mentioning that there is no change in the affinity of the substrate for the enzyme. It's just that the enzyme has been inactivated because of this covalent complex between the enzyme and the inhibitor. So now how does this compare to each of the types of reversible inhibition? Well, when it comes to competitive reversible inhibition, what happens is that the KM is actually going to increase because the affinity of the enzyme for the substrate is going to decrease because the inhibitor is present V max. On the other hand, will not be affected in the case of competitive inhibition. Now, by contrast, noncompetitive inhibition will decrease the maximum rate of the reaction without affecting KM. So without affecting substrate affinity for the enzyme. Now, uncompetitive inhibition, on the other hand, will decrease both V max and KM. So it decreases both the maximal reaction rate and also the substrate affinity. So what is the main point here? Well, all this is to say that the reason why the effects of each type of inhibition are different is because of what type of interaction is present between the inhibitor and the enzyme. Going back. Now to our answer choices, our correct answer is going to be option B which reads as follows it says irreversible inhibitors form a covalent bond with the enzyme permanently inactivating it. While reversible inhibitors bind non covalent, allowing for temporary inhibition to be reversed. And there you have it. So with that being said, thank you so very much for watching. And I hope you found this helpful.

How does an irreversible inhibitor function differently than a reversible inhibitor?

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Key Concepts

Irreversible Inhibitors

Reversible Inhibitors

Mechanisms of Inhibition