Enzyme Inhibitors: Videos & Practice Problems

Enzyme inhibitors are crucial for regulating enzymatic activity, either by decreasing it or stopping it altogether. There are two main types: irreversible inhibitors, which bind covalently and permanently deactivate enzymes (e.g., nerve gas), and reversible inhibitors, which bind non-covalently and can be released. Reversible inhibitors can be competitive, competing with substrates for the active site, or non-competitive, binding to a different site and altering the enzyme's shape. Understanding these mechanisms is essential for grasping enzyme regulation in biochemical processes.

Enzyme Inhibition

Hi. In this video, we're going to be talking about enzyme inhibition. So, what do enzyme inhibitors do? Well, they decrease enzymatic activity. And, you can imagine why that needs to happen. Enzymes speed up reactions, but we don't always need reactions speeded up. Sometimes, we need them stopped. And in the cases that we need them stopped, we need things that can regulate enzymes, and these are typically enzymes inhibitors. So, there are 2 main types of enzyme inhibitors. These can be reversible or irreversible. So irreversible inhibitors actually bind so tightly to the enzyme through covalent bonds. And because they're bound so tightly, they just inhibit the function, and, you know, never let go. So, these are really irreversible. The enzyme will never be activated again. So, a good example of this is actually nerve gas, which, you know, is lethal. And that's because it binds to these enzymes and it never lets go and it ends up in death. It doesn't have to end up in death. Not all of our irreversible inhibitors end up in death, but, a lot of them do, because you have to be able to reverse it to control and regulate the reaction. Now, the second type is the reversible inhibitors, and these bind more weakly, usually through non-covalent interactions. And because they bind weakly, that means that they are reversible. So, those bonds and those non-covalent interactions can be broken, so that they can release their inhibitory effect. They will also be referred to as allosteric. And, essentially the competitive ones do exactly what you would think, they compete with the substrate for the active site. And the non-competitive ones, or the allosteric, do not compete with the substrate for the active site. So, I'm going to show you an image to really get those definitions down. But, first, I want to say that enzymes are crucial for the regulation of cellular chemical reactions. But like I said before, they can be harmful, things like nerve gas and stuff, but they're very important for regulation. So now, let's look at different types of inhibition of enzymes. So, first, we have the normal, enzyme experience or reaction. So the enzyme here, the substrate here, they bind, and that makes products, or yeah, products that are released. Now if we want to inhibit an enzyme, we can do this competitively or non-competitively. So, through the competitive approach, you can see that there is this inhibitor here that actually binds to the same place that the substrate binds. So, when the substrate comes in and tries to bind, it's unable to. And, that actually inhibits it. Now, for the non-competitive, you can see that the inhibitor comes in and actually binds to this separate site. So, that when the enzyme, the substrate comes in, it is found that its active site has actually changed shape. As you can see here, where it's this corner formation, while it was this boxy formation. So, the substrate no longer fits, or it's no longer attracted to the enzyme, but, and so it somehow inhibits the product formation and the chemical reaction occurring. So, those are two forms of reversible enzyme inhibition. So, now let's move on.

Which of the following enzyme inhibitors binds through covalent bonds?

• A. Reversible
• B. Irreversible

Answer: (B)

Which of the following enzyme inhibitors binds to the enzymes active site to inhibit the enzyme?

• A. Reversible
• B. Irreversible
• C. Competitive
• D. Non-Competitive

Answer: (C)

Here’s what students ask on this topic:

What are enzyme inhibitors and why are they important?

Enzyme inhibitors are molecules that decrease or stop the activity of enzymes. They are crucial for regulating biochemical reactions within cells. Enzymes speed up reactions, but not all reactions need to be continuously active. Inhibitors help control these reactions, ensuring they occur only when necessary. There are two main types of enzyme inhibitors: irreversible and reversible. Irreversible inhibitors bind covalently to enzymes, permanently deactivating them. Reversible inhibitors bind non-covalently and can be released, allowing the enzyme to regain activity. Understanding enzyme inhibitors is essential for studying cellular processes and developing drugs that can modulate enzyme activity.

What is the difference between competitive and non-competitive inhibition?

Competitive inhibition occurs when an inhibitor competes with the substrate for the enzyme's active site. The inhibitor binds to the active site, preventing the substrate from binding and thus inhibiting the enzyme's activity. Non-competitive inhibition, on the other hand, involves the inhibitor binding to a different site on the enzyme, known as the allosteric site. This binding changes the enzyme's shape, making the active site less effective or inactive for substrate binding. Both types of inhibition are reversible, but they differ in their mechanisms and effects on enzyme activity.

How do irreversible inhibitors affect enzyme activity?

Irreversible inhibitors bind covalently to enzymes, forming a stable, permanent complex that deactivates the enzyme. This binding is so strong that the enzyme cannot regain its activity, effectively stopping the biochemical reaction it catalyzes. An example of an irreversible inhibitor is nerve gas, which binds to enzymes in the nervous system, leading to lethal consequences. While not all irreversible inhibitors are harmful, their permanent nature makes them powerful tools for studying enzyme function and developing certain types of drugs.

Can you explain the role of reversible inhibitors in enzyme regulation?

Reversible inhibitors play a crucial role in enzyme regulation by temporarily decreasing enzyme activity. They bind non-covalently to enzymes, allowing them to be released and the enzyme to regain activity. There are two main types of reversible inhibitors: competitive and non-competitive. Competitive inhibitors compete with the substrate for the active site, while non-competitive inhibitors bind to an allosteric site, altering the enzyme's shape and function. This reversible binding allows cells to finely tune enzyme activity in response to changing conditions, maintaining metabolic balance.

What are some examples of enzyme inhibitors used in medicine?

Enzyme inhibitors are widely used in medicine to treat various conditions. For example, ACE inhibitors are used to treat high blood pressure by inhibiting the angiotensin-converting enzyme, which regulates blood pressure. Another example is protease inhibitors, used in antiviral therapies for HIV, which inhibit the viral protease enzyme necessary for viral replication. Statins, used to lower cholesterol levels, inhibit HMG-CoA reductase, an enzyme involved in cholesterol synthesis. These inhibitors help manage diseases by modulating specific enzyme activities, demonstrating the therapeutic potential of enzyme inhibitors.