Question

Hi,
Can someone please help me with the following biology question? Thank you! :)

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QUESTION 49.

You're a college student working a biology laboratory during a summer research internship. In your lab, the enzyme catalase was studied in the presence of two types of enzyme inhibitors. Results are shown in the following table:

Average Catalase Rates (in mL O₂ / minute) at pH 6.5 Using Two Inhibitors

Peroxide Stock (mM)	No Inhibitor	+ Inhibitor A	+ Inhibitor B
25	7.6	3.2	3.7
100	31.9	10.8	28.6
150	32.3	12.2	32.0

From the above data, what is the main conclusion you can draw on the type of inhibition for molecules A and B on catalase?
Identify which molecule is competitive or non-competitive. Briefly Explain.

Answer 1

According to the question:-

A hypothetical reaction can be assumed as-

Peroxide substrate is getting converted into water and nascent oxygen in presence of catalase enzyme.

From the data provided it can be observed that-

In case of inhibitor A, when the peroxide stock is added, the average catalase rates are remaining lower than that of average catalase rates in case of no inhibitor added, even at higher concentration of peroxide substrate. Thus it can be concluded that Inhibitor A is showing non-competitive type of enzyme inhibition.

While in case of inhibitor B, when the peroxide stock is added, the average catalase rates are getting closer value to the average catalase rates in case of no inhibitor added, as the higher concentration of peroxide substrate is used. Thus it can be concluded that Inhibitor B is showing competitive type of enzyme inhibition.

Explanation: In case of competitive type of inhibition, an inhibitor has a structure similar enough to the substrate so that it can bind with the enzyme at its active site with higher affiinity. In this case, when higher concentration of substrate is used, Vmax value can be closer to the normal Vmax value where no inhibitor is used. (Compare the data of no inhibitor and inhibitor B in the question).

But, In case of non-competitive type of inhibition, an inhibitor has the capacity to bind with the active site of enzyme and thus blocks its catalytic power, so that a substrate can not bind with the enzyme at its active site. In this case, even when higher concentration of substrate is used, Vmax value can not be closer to the normal Vmax value where no inhibitor is used. (Compare the data of no inhibitor and inhibitor A in the question).