Question

1 Consider this graph that we talked discussed in class on how an enzymes affects the rate of product formation. Catalyzed Uncatalyzed reaction Substrate concentration Now consider you have discovered an allosteric inhibitor of the enzyme. You do this experiment again, adding enough allosteric inhibitor to block 50% of the enzyme activity present in the reaction. a. Thinking in terms of the models shown in class, what does it actually mean in molecular terms when "50% of the enzymatic activity" is blocked? (1 pt) b. In the above graph, draw in the curve of "catalyzed reaction + inhibitor". Assume 50% inhibition of enzymatic activity. In drawing your curve consider where the plateau occurs (if it occurs), in terms of "substrate concentration" and "rate of product formation. 5 pts

Answer 1

Please find the answers below:

Answer a: An enzyme catalyzed reaction must be understood with the fact that the active sites of the enzyme are filled with the substrate to give rise to a product. However, since no enzyme is fully saturated with the substrate under physiological conditions, the quantitative analysis is performed by the assumption that at least 50% of the active sites are covered with substrate. Similarly, when inhibitors are being studied, similar notion is still followed that 50% of the total enzyme catalysis is prohibited using the inhibitor. Technically, it means that 50% activity available from the enzymes's maximum efficiency has been already blocked. Thus, this helps not only in understanding but also in making calculations.

Answer b: The inhibitor modulated enzyme catalysis can be graphically interpreted as below:

Negative allosteric inhibitor Normal catalysis 乒.). Substrate concentration

Here, the curve of the allosteric inhibitor would be found down-wards as compared to normal since this allosteric inhibitor is a negative regulator of enzyme catalysis.