MCAT® ExamBiological and Biochemical Foundations of Living SystemsHard
A research team is investigating the properties of a recently isolated protein. They observe that the protein's catalytic activity significantly increases in the presence of a specific small molecule, even though this molecule does not bind to the enzyme's active site. Instead, it binds to a distinct regulatory site, inducing a conformational change that enhances substrate binding and turnover. This phenomenon is an example of:
- AAllosteric activation
- BNon-competitive inhibition
- CIrreversible inhibition
- DCompetitive inhibition
Show answer & explanationAnswer & explanation
Correct answer: A. Allosteric activation
Allosteric regulation involves a molecule binding to an enzyme at a site other than the active site, inducing a conformational change that alters the enzyme's activity. In this case, the small molecule increases activity, making it allosteric activation.
Why the other options are wrong
- B. Non-competitive inhibition involves a molecule binding to an allosteric site, reducing enzyme activity without competing for the active site.
- C. Irreversible inhibition typically involves a covalent modification that permanently inactivates the enzyme.
- D. Competitive inhibition involves a molecule binding to the active site, competing with the substrate.
Allosteric Regulation
Regulation of an enzyme's activity by the binding of a molecule (effector) at a site other than the active site, inducing a conformational change that alters enzyme affinity or catalytic efficiency.
- Effector binds to a regulatory (allosteric) site.
- Causes conformational change in the enzyme.
- Can be activation or inhibition.
- Often involved in feedback loops.
Memory trick: Allosteric: Another Site, Another Shape, Another Speed