How can you distinguish between a competitive inhibitor and an uncompetitive inhibitor experimentally?

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All right. Hello everyone. So this question is a true or false. A competitive inhibitor can be identified from an uncompetitive inhibitor by increasing the substrate concentration and monitoring the reactions rate change. Option A says true and option B says false. All right. So generally speaking, recall that inhibitors are species that are going to interfere with an enzyme's activity in some way. So depending on how it does, so inhibitors can receive different names. For example, for this question, we can distinguish between a competitive inhibitor and an uncompetitive inhibitor. But before we talk about these specific definitions, let's just recall a few properties about enzymes in general. In normal conditions, the enzyme reacts with its specific substrate to form a species known as the enzyme substrate complex in which those two things are combined together. After the reaction is catalyzed, you get your product with the free enzyme to repeat this process once more. But here we're just focusing on interactions between the enzyme and the substrate. Now, in the presence of an inhibitor, the enzyme can do the same thing this time. Now, the enzyme can react with the inhibitor to create an enzyme inhibitor complex. So here, when we talk about a competitive inhibitor, we are talking about exactly what was described previously. So essentially you have the inhibitor competing directly with the substrate or binding with the enzyme itself. Now, this is the important distinction here, a competitive inhibitor is going to inhibit the activity of the enzyme by competing with the substrate for the same active site on the enzyme. They're competing for the same spot. Now, the same cannot be said for an uncompetitive inhibitor because the uncompetitive inhibitor is going to bind rather to the enzyme substrate complex. So when it binds to the enzyme substrate complex, we get what's known as an enzyme substrate inhibitor complex. So now what's important to recognize here is that at no point does an uncompetitive inhibitor actually compete with the substrate directly? And so that means that increasing the substrate concentration is not going to affect on competitive inhibition. It is however, going to impact competitive inhibition because when the substrate concentration reaches a certain point, it's going to essentially overpower the inhibitor, right. So they're if there's more of the substrate available in solution, then that's going to outcompete the inhibitor itself, which means that eventually the reaction rate is going to return to normal. And so the answer here is true, right? Because increasing the substrate concentration is going to impact the reaction rate for a competitive inhibitor, but not for the uncompetitive inhibitor. And so with that being said, thank you so very much for watching. And I hope you found this helpful.

How can you distinguish between a competitive inhibitor and an uncompetitive inhibitor experimentally?

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Key Concepts

Competitive Inhibition

Uncompetitive Inhibition

Enzyme Kinetics