Question

Consider the following data:

Enzyme	$K_m$ (mM)
A	0.02
B	0.2
C	0.002

Which of the following arrangement is correct with respect to their affinity towards a substrate of the given enzymes?

• A. A>B>C
• B. B>C>A
• C. C>A>B
• D. B>A>C

Answer 1

The correct option is C C>A>B

The catalytic efficiency of two different enzymes can be compared by their K${}_m$ values. The K${}_m$ or the Michaelis-Menten constant refers to the concentration of substrate at which the reaction reaches half its maximum velocity.

K${}_m$ indicates the affinity of the enzyme for its substrate. A high K${}_m$ value indicates low affinity while low K${}_m$ value indicates a high affinity for the substrate. A higher affinity for the substrate corresponds to higher efficiency of enzymes, since high affinity ensures greater amount of substrate-enzyme binding and product formation.

K${}_m$ suggests that an enzyme is able to tightly bind with the substrate. From the given table C has the least value of K${}_m$ followed by A and B has the highest K${}_m$ value. Hence, the correct arrangement of the enzymes with respect to their affinity towards substrate is: C>A>B.