Non-competitive, reversible allosteric inhibitors

So far we have discussed inhibitors which bind to the active site and prevent the natural substrate from binding. We would therefore expect these inhibitors to have some sort of structural similarity to the natural substrate. We would also expect reversible inhibitors to be displaced by increased levels of natural substrate. 

However, there are many enzyme inhibitors which appear to have no structural similarity to the natural substrate. Furthermore, increasing the amount of natural substrate has no effect on the inhibition. Such inhibitors are therefore noncompetitive inhibitors, but unlike the non-competitive inhibitors mentioned above, the inhibition is reversible. 

Adding more substrate will not reverse the situation, but that does not mean that the inhibition is irreversible. Since the inhibitor uses non-covalent bonds to bind to the allosteric binding site, it will eventually depart in its own good time. 

But why should there be this other binding site  

The answer is that allosteric binding sites are important in the control of enzymes. A biosynthetic pathway to a particular product involves a series of enzymes, all working efficiently to convert raw materials into final product. Eventually, the cell will have enough of the required material and will want to stop production. Therefore, there has to be some sort of control which says enough is enough. The most common control mechanism is one known as feedback control, where the final 

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