Enzyme Inhibition - Online Tutor, Practice Problems & Exam Prep

Enzyme Inhibition

Hey, guys. In this video, we're going to introduce enzyme inhibition. So enzyme inhibition is really caused by compounds called enzyme inhibitors, and enzyme inhibitors are commonly abbreviated with the letter I just like we see here. And so really these enzyme inhibitors, just like we already said, are really just specific compounds that interfere with product formation and therefore decrease an enzyme's initial reaction rate or the v₀ of an enzyme-catalyzed reaction. Now moving forward in our course, we're going to talk about many different types of enzyme inhibitors, but one thing that they all share in common is that they all decrease an enzyme's initial reaction velocity or essentially they slow down or inhibit the enzyme-catalyzed reaction. Now these enzyme inhibitors can actually form a complex with either the free enzyme, which recall is abbreviated with the letter E and is just the enzyme that is not bound to any substrate. And or the inhibitor could also form a complex with the already formed enzyme substrate complex to inhibit the reaction and again decrease the enzymes initial reaction velocity. Now, depending on the type of inhibitor, the inhibitor will either only bind to the free enzyme or it will only bind to the enzyme substrate complex, but some inhibitors will actually bind to both the free enzyme and the enzyme substrate complex. And again, what determines that is the type of inhibitor. And, again, later in our course, we'll talk about these different types of inhibitors. But for now, notice that down below in our example image we're showing you how the free enzyme inhibitor complex can form over here on the left hand side, but it's also possible for the enzyme substrate inhibitor complex to form and that's what we're showing over here. And so with the enzyme inhibitor complex, notice that in some cases the inhibitor can interact with the free enzyme that is not bound to any substrate. And, of course, this is going to form the free enzyme inhibitor complex or the EI complex for short as shown here. Now, other types of inhibitors notice they will allow the free enzyme in the substrate to form the enzyme substrate complex as normal, but then the inhibitor will interact with the enzyme substrate complex to form the enzyme substrate inhibitor complex or the ESI complex for short. And again, it's going to depend on the type of inhibitor whether or not it's just the EI, the E just the ESI or both that are formed. Now, the question does arise of why is it that a cell would want to decrease the enzymes initial reaction rate? Well, it turns out that biological enzyme inhibitors can be used by cells to regulate enzyme activity. But they can also be used by cells to act as defense poisons and protect the cells from pathogens. Now, enzyme inhibitors we'll also see moving forward, are also important for medicine since doctors can use them as drugs to treat diseases. Now notice down below in our image over here on the left hand side, we're showing you how cells can use enzyme inhibitors for regulation of enzyme activity. And so notice down below we have a eukaryotic cell and this green circle over here and inside of our eukaryotic cell we have this enzyme catalyzed reaction. And notice that this enzyme catalyzed reaction has gotten a bit carried away and it's produced a lot of product over here. And the cell is able to recognize that, and so notice that the cell here is actually saying, okay, enzyme, referring to this enzyme and this enzyme catalyzer reaction over here, and it's saying, okay, enzyme. I think we have enough product. So I'm gonna slow you down a bit with some inhibitor. And so the eukaryotic cell is able to produce inhibitor and the inhibitor is able to act within the cell to regulate its own enzymatic reaction. And so, as we said up above, depending on the type of inhibitor, the inhibitor can either interact with the free enzyme to form the EI complex or the inhibitor could interact with the enzyme substrate complex, to form the ESI complex. And again, that's gonna depend on the type of inhibitor that's produced. But either way, you can see that enzymes, activity are able to be regulated by these inhibitors. Now notice over here on the right hand side, we're showing you how enzyme inhibitors can also be used by cells to act as poisons in defense. So these inhibitors can act as defense mechanisms, for protection reasons. And so notice down below in our image we have a harmful bacteria over here on the top left in brown, and notice that within the harmful bacteria there is an enzyme catalyzed reaction and this harmful bacteria is saying I'm taking you down to our eukaryotic cell over here in green, but notice that the eukaryotic cell is saying, not so fast bacteria, inhibitor protect me. And so notice in this scenario, the eukaryotic cell is actually secreting or expelling, inhibitor into the environment so that the inhibitor can act as a poison and defend the eukaryotic cell. And so, this inhibitor that is secreted or released into the environment can actually make its way into the harmful bacteria and again, depending on the type of inhibitor, it can either interact with the free enzyme, to form the EI complex or it could interact with the enzyme substrate complex to form the ESI complex. But in either scenario, this reaction will be inhibited and that could kill or at least, inhibit the harmful bacteria and that will protect the eukaryotic cell. And so these are some ways that biological enzyme inhibitors can be used by cells. Now, again, as we've already mentioned, there are actually several different categories of enzyme inhibitors. And so moving forward in our course, we're going to talk about each of these different categories of enzyme inhibitors and these include irreversible inhibitors also known as inactivators, reversible inhibitors, competitive inhibitors, uncompetitive mixed, and noncompetitive inhibitors. And so, again, as we move forward our course, we're gonna talk about each of these different types of enzyme inhibitors 1 by 1. And so this here concludes our introduction to enzyme inhibition and we'll be able to learn more and more about it as we move along in our course. So I'll see you guys in our next video.

How can inhibitors prevent an enzyme from functioning normally?

• A. Binding to the free enzyme.
• B. Binding to the ES-complex.
• C. Blocking the active site.
• D. Altering the active site.
• E. Destroying the enzyme.
• F. All options are true.

Which of the following statements is false regarding inhibitors & enzyme-catalyzed reactions?

• A. The V_max of an enzyme-catalyzed reaction will never increase in the presence of an enzyme-inhibitor.
• B. Enzyme inhibitors can be secreted via exocytosis to defend against harmful threats.
• C. At saturating [S], the rate is directly proportional to [enzyme].
• D. The E_A for catalyzed & uncatalyzed reactions are equal, but the K_eq is more favorable in a catalyzed reaction.
• E. Binding of an inhibitor to an enzyme can be reversible or irreversible.