Good day my Biochem peeps,
Enzyme Inhibition by FortuneFavorsPrep
In your revision, you must be like me where you are wondering why you can never remember the enzyme kinetics and the graphs seen in the different reversible inhibition methods. Well, I came across this video where the person explains competitive, non-competitive and uncompetitive inhibition.
The guy on this video gives a good summary of each method and gives the main features of each inhibition, the main effects on the Km and Vmax of the enzyme and the mechanism of action of the inhibitor. He then actively draws both the M-M curve and L-B plot for each of the inhibition described. He is showing you why there is a change in the value, how to draw it and what the plot and curve changes means.
This video is well explained and an incentive to studying the inhibition since it summarizes most of what you need to know on the topic for exams. I felt that this video was an apt summary of the topic and there were little flaws in the explanation or demonstration. However, I felt that explanation of mixed inhibition and irreversible inhibition should also be covered. There were also no examples of each type of inhibitor. Nevertheless, this does not take away from the efficacy of the video and I enjoyed it a lot since above all, it was a short video of about 15 minutes.
The main points of the video has been summarized below, however, I am strongly suggesting that you view this video since it will really help you, if you are still confused on the topic and you wanted a nice summary of the essentials of inhibition.
The video begins with a summary of inhibitors. He then begins to describe competitive inhibition and the fact that the inhibitor binds to the active site of the enzyme and competes with the substrate to bind. He illustrates the equation of the enzyme and substrate interaction and shows the effect of a competitive inhibitor on this process. The guy then goes on to explain the effect of this inhibitor on the affinity of the enzyme for the substrate and hence an increase in the Km value. He also mentions that this inhibition may be reversed or overcome by increasing the substrate concentration and hence does not affect the Vmax. Finally, he uses the M-M curve and L-B plot to illustrate what was explained in the text of the video. He drew the two graphs, which was good since it actually demonstrated the method and reason for the position of the points on the graphs.
Then he moved on to non-competitive and uncompetitive inhibition where he proceeded to explain the main points of these two types of inhibition and compared them to competitive inhibition. In summarizing non-competitive, he mentions that this inhibitor binds to a site other than the active site and changes the conformation of the enzyme. He links this to induced fit model mechanism of action and then compares this method to that of competitive inhibition. He then further details the change in the Vmax and Km. He aptly explains that non-competitive inhibition does not prevent the substrate from binding to the enzyme and therefore does not change the affinity of the enzyme for the substrate and hence the Km is changed. However, since it changes the conformation of the enzyme, it decreases the ability for product formation and hence decreases the rate of reaction of the enzyme. This means that Vmax is decreased. Finally, he ends this section by draw the L-B plot and shows the changes that the non-competitive inhibitor has on the enzyme kinetics.
This video ends with an explanation of uncompetitive inhibition. In this final segment, he illustrates again the graphs and show how there is a decrease in the Vmax and Km due to the inhibitor binding to the enzyme-substrate complex. However, he does not mention that this is a proportional decrease and goes into why there is a decrease in these values. He also does not mention that uncompetitive inhibitor may bind to the free enzyme at another site than the active site. But overall, the explanation and illustration was very helpful in visualizing and conceptualizing the topic.
Well, I really hope that this aids in your revision. A point to note is that this should not be taken as the only source on this topic and you should refer to Sir’s lectures and the textbook for further details. Happy studying until the next one….