While comparing two inhibitors, can we check how they alter the Km and Vmax of the reaction and then decide which inhibitor is more potent.

I tried explaining in this way:

While I think the answer should be "no", I am not entirely sure. I got these statements from Wikibooks :

Competitive inhibitors can only bind to E and not to ES. They increase Km by interfering with the binding of the substrate, but they do not affect Vmax because the inhibitor does not change the catalysis in ES because it cannot bind to ES. Uncompetitive inhibitors can only bind to the ES complex. Therefore, these inhibitors decrease Km because of increased binding efficiency and decrease Vmax because they interfere with substrate binding and hamper catalysis in the ES complex Mixed inhibitors can bind to either E or ES complex, but have a preference for one or the other. This can either increase or decrease Km, respectively. Both cause a decrease in Vmax. Non-competitive inhibitors have identical affinities for E and ES. They do not change Km, but decreases Vmax.

From this it is shown that the inhibitors do affect Vmax and Km. But I can't figure out a way to compare them. Any help?

  • 2
    $\begingroup$ Why do you think the answer "should be 'no'"? You can certainly compare two inhibitors of the same "class", that is: either compare two competitive or two uncompetitive inhibitors. If competitive inhibitor A increases $K_{\rm M}$ by $10\%$ and competitive inhibitor B by $50\%$, then – obviously – inhibitor B is more potent than A. $\endgroup$
    – Domen
    Feb 10, 2022 at 15:21
  • 2
    $\begingroup$ The kinetics of enzyme inhibitors is a basic aspect of biochemistry that is treated in almost every textbook on the subject and can be found in numerous resources for students — PowerPoint slides, lecture notes and the like. Just search for "Enzyme Inhibitors Lecture Notes" or the like. Then decide what it is you want to compare. One competitive inhibitor with another? One non-competitive inhibitor with another? Or something else? Clearly you cannot compare different types of inhibitor. You need to clarify your problem before you can answer it. $\endgroup$
    – David
    Feb 11, 2022 at 20:59


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