Enzyme Inhibitors

Modulators, moderators, or modifiers refer to compounds that influence the rates of enzyme-catalyzed reactions. The effect of enzyme inhibitors is usually to reduce the rate, while the enzyme activators can increase the rate of enzyme reaction. The molecular events leading to the experimentally observed effects has to be understood when studying these phenomena. A basic explanation for the so-called mechanism or mode of action of a substance on the enzymic reaction can be studied by a number of techniques under investigation. Although the methods for solving the 3-D structure of enzyme-inhibitor complexes result in clear steric presentations, and quantum mechanical calculations provide data consistent with basic physicochemical laws, the great practical value of classical kinetic information cannot and must not be neglected. In addition, not only the mode of action of an inhibitor is important, but also its effects on the substrate turnover provide information that cannot be obtained from studies of pure enzyme substrate systems.

According to the basis of enzyme kinetics, enzyme inhibitors can be divided into two groups. One group consists of reversible inhibitors that form noncovalent interactions with various parts of the enzyme surface, which can be easily reversed by dilution or dialysis. The other group consists of irreversible inhibitors that interact with different functional groups on the enzyme surface by forming strong covalent bonds that often persist even during complete protein breakdown.

Reversible Inhibitors

Based on the relation between the velocities of the inhibited and uninhibited reactions, reversible inhibitors can be divided into three types: noncompetitive type, competitive type and uncompetitive type. The degree of inhibition is unaffected by change in the substrate concentration in the pure noncompetitive type, reduced at higher substrate concentration in the competitive type, and increased by increasing substrate concentrations in the so-called coupling, or uncompetitive behavior.

Although the different types of inhibition imply ideas about the mechanism of inhibitor action, they cannot necessarily be interpreted in terms of the molecular events described by the particular type. Nevertheless, it is expected that structural similarities between the substrate and the inhibitor exclude simultaneous binding, leading to a reduction of the degree of inhibition with increasing substrate concentration and, thus, to competitive inhibition. On the other hand, if the two can become attached to the enzyme simultaneously, their structures are unlikely to be similar so that they do not compete, and the inhibition is termed noncompetitive.

Irreversible Inhibitors

Irreversible inhibitors are compounds that interact with the enzyme in such a way as to cause permanent loss of activity. They can make stable covalent bonds with the enzyme active-site residues, therefore they are referred to as catalytic poisons. If such binding occurs, the inhibitors are needed only in trace amounts because each inhibitor molecule eventually finds its own enzyme molecule and abolishes the latter’s activity. In practice, the formation of a stable covalent bond is so slow that the rate of inactivation can usually be determined by following the time course of residual enzyme activity, after various preincubation times with the inhibitor, even under conditions when the inhibitor is in great excess. Consequently, if the reaction is started by the addition of the enzyme, the initial activity would be unaffected by the presence of such an inhibitor. Sometimes, however, every encounter of the inhibitor with the enzyme does not lead to successful bonding. In such cases, irreversible inactivation is preceded by a reversible step, similar to the classical reversible inhibition.

Related Products at Creative Enzymes:

Enzyme Inhibitors

Related Services at Creative Enzymes:

Screening of Substrates, Inhibitors, and Other Ligands


Wiederschain G Y. Enzymes and their inhibition. Drug development [J]. Biochemistry, 2006, 71(5):582-582.


  1. I am writing to make you understand what a terrific experience my friend’s child developed going through yuor web blog. She realized several details, which included what it is like to possess a marvelous coaching mindset to get folks without difficulty gain knowledge of several problematic matters. You truly did more than people’s expected results. Thanks for distributing these invaluable, trustworthy, revealing and as well as fun thoughts on that topic to Julie.

  2. I must get across my gratitude for your generosity supporting folks who actually need guidance on that subject matter. Your special dedication to passing the solution up and down had been extremely powerful and have in most cases enabled guys much like me to arrive at their goals. Your useful instruction can mean a whole lot to me and further more to my colleagues. Warm regards; from everyone of us.

  3. I needed to draft you that very small remark so as to say thanks a lot over again with the pleasing knowledge you’ve shared on this site. It was seriously generous with you to deliver easily all that some people could possibly have offered for sale for an e book in making some profit for their own end, most notably given that you could possibly have done it if you considered necessary. Those tricks in addition acted to be the great way to fully grasp that the rest have a similar desire just as mine to understand more with regards to this condition. Certainly there are some more pleasant moments up front for those who see your site.

  4. I intended to draft you one very small word so as to thank you very much again relating to the exceptional strategies you’ve shown at this time. This has been quite strangely generous of you in giving freely exactly what a few people could possibly have marketed as an electronic book to earn some cash for themselves, principally seeing that you could have done it in case you decided. The solutions as well worked like the good way to understand that other people have similar eagerness just like my own to see good deal more in regard to this condition. Certainly there are lots of more pleasurable moments up front for individuals who looked at your website.

  5. Needed to create you one very little remark so as to say thanks a lot the moment again regarding the splendid basics you have discussed on this page. It was simply unbelievably generous of you to make unreservedly precisely what many individuals could possibly have advertised as an ebook in order to make some profit on their own, principally considering the fact that you might well have tried it in the event you desired. These solutions additionally worked to become a easy way to realize that some people have the identical desire just like mine to grasp many more with reference to this condition. I’m certain there are lots of more enjoyable occasions up front for people who examine your blog post.

  6. I wish to express my passion for your generosity for folks who need assistance with in this matter. Your very own commitment to passing the message all over appears to be rather functional and have always helped women just like me to reach their objectives. Your personal helpful guideline implies much a person like me and a whole lot more to my fellow workers. Thanks a lot; from each one of us.

  7. I want to express thanks to this writer for rescuing me from this type of crisis. After surfing around through the the web and obtaining methods which were not productive, I believed my entire life was well over. Living devoid of the approaches to the problems you’ve sorted out as a result of the guideline is a crucial case, as well as those that could have negatively affected my career if I hadn’t discovered your blog. Your personal understanding and kindness in touching all things was valuable. I am not sure what I would’ve done if I hadn’t discovered such a subject like this. It’s possible to now relish my future. Thanks for your time very much for the high quality and amazing help. I will not think twice to endorse your web blog to any individual who would like support on this issue.

  8. Thanks for all your hard work on this web page. Kim really loves carrying out research and it is easy to see why. Many of us hear all of the powerful means you produce functional ideas on your website and even strongly encourage participation from other individuals on the situation while our favorite princess is in fact understanding a whole lot. Enjoy the remaining portion of the year. You are always doing a dazzling job.

  9. Thank you so much for providing individuals with remarkably spectacular possiblity to discover important secrets from this blog. It’s usually so pleasant plus full of fun for me and my office colleagues to search your web site the equivalent of three times weekly to learn the fresh guidance you have. And definitely, I’m so actually happy considering the staggering knowledge served by you. Certain 2 facts in this article are surely the most efficient we’ve had.

  10. I’m writing to make you know what a magnificent discovery my girl obtained going through the blog. She came to understand lots of issues, most notably what it’s like to have a wonderful helping nature to let others with no trouble learn about some impossible topics. You truly surpassed her expectations. Thanks for imparting these priceless, trustworthy, informative and also fun thoughts on the topic to Janet.

  11. I actually wanted to type a quick word so as to thank you for some of the magnificent recommendations you are showing on this site. My considerable internet research has at the end of the day been recognized with pleasant concept to talk about with my family. I ‘d admit that we site visitors are very endowed to live in a good website with many perfect individuals with valuable opinions. I feel very fortunate to have seen your entire website page and look forward to tons of more pleasurable moments reading here. Thank you again for a lot of things.

Leave a Reply

Your email address will not be published.