In this video, we're going to introduce enzyme inhibition. Recall that enzymes are all about speeding up chemical reactions. But sometimes the reactions might be going too fast, and the cell might need to stop the enzyme from going so fast. In that case, enzyme inhibition can be useful. Enzyme inhibitors are defined as compounds that interfere with and selectively inhibit the catalysis of specific enzymes. Enzyme inhibitors can be used to slow down enzymes if they're going too fast. Now, there are 2 types of inhibitors that we're going to introduce here in this video, and those two types are listed down below. The first type are the competitive inhibitors and the second type that we're going to introduce are non-competitive inhibitors. Now competitive inhibitors, as their name implies with the competitive part, are going to compete with the substrate for a position in the free enzyme's active site. Competitive inhibitors can only bind to the enzyme and compete with each other for a binding spot in the active site of the enzyme. Let's take a look at our image down below over here on the left-hand side at competitive inhibition. Notice that the enzyme is shown in red, and in blue what we're showing you is the competitive inhibitor. It's called a competitive inhibitor because it's going to compete with the substrate over here, which is in black, for a position in the enzyme's active site. If the competitive inhibitor binds to the enzyme's active site before the substrate does, then the competitive inhibitor is going to block the substrate from binding to the active site as we can see over here. Notice that the competitive inhibitor is binding to the active site of the enzyme and it binds to the active side of the enzyme, it is preventing the normal substrate from binding and if the normal substrate cannot bind, then that means that catalysis is going to be prevented, and the enzyme's reaction is going to essentially slow down and be inhibited.
The second type of inhibitor that we're going to talk about are non-competitive inhibitors. As their name implies, they are non-competitive, so they do not compete with the substrate for a position in the active site. Instead, the non-competitive inhibitor is going to bind to what's known as an allosteric site. The allosteric site on an enzyme is defined as an alternative site for an inhibitor binding that is not going to be the active site. Let's take a look at our image down below over here on the right-hand side to get a better understanding of non-competitive inhibition. Notice that the non-competitive inhibitor is shown here in purple, so we can go ahead and label it as the non-competitive inhibitor. Notice, the noncompetitive inhibitor is not going to compete with the substrate over here for a binding position in the active site. Instead, the noncompetitive inhibitor is going to bind to a completely different site over here that we have in blue, and this site is referred to as the allosteric site. When an inhibitor binds to the allosteric site of an enzyme, it can cause the enzyme to change its shape, to alter its shape. When it alters its shape, it's going to also alter the shape of the active site. Notice that the active site here is taking on a different shape than what it used to have before the noncompetitive inhibitor bound. The active site will change in such a way that it will prevent the substrate from binding to the enzyme. If the substrate cannot bind to the enzyme, then that is going to prevent or inhibit catalysis and slow down the enzyme. These inhibitors can be used to slow down and inhibit enzymes. This here concludes our introduction to enzyme inhibition as well as the competitive and noncompetitive inhibitors, and we'll be able to get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.
