A mutation that results in a single amino acid substitution in the active site of an enzyme
A) may alter the ability of a noncompetitive inhibitor to bind to the enzyme.
B) may alter the ability of an allosteric regulator to alter enzyme activity.
C) may change the substrate specificity of the enzyme.
D) may alter the ∆G for the reaction catalyzed by the enzyme.

Question

Quizplus · Accepted Answer

The active site of an enzyme is responsible for binding and catalyzing specific substrates. A mutation that results in a single amino acid substitution in the active site may alter the shape and charge of the active site, which can change the substrate specificity of the enzyme. This means that the enzyme may no longer be able to properly bind and catalyze its original substrate, but may instead bind and catalyze a different substrate. This change in substrate specificity can have significant implications for the function of the enzyme and the biological processes it is involved in.

Option A is incorrect because noncompetitive inhibitors bind to a different site on the enzyme than the active site, so a mutation in the active site would not affect their ability to bind.
Option B is incorrect because allosteric regulators bind to a separate allosteric site on the enzyme, not the active site, so a mutation in the active site would not affect their ability to affect enzyme activity.
Option D is incorrect because a single amino acid substitution in the active site may alter the rate at which the enzyme catalyzes the reaction, but would not directly affect the free energy change (∆G) of the reaction itself.

A Mutation That Results in a Single Amino Acid Substitution