MCAT® ExamBiological and Biochemical Foundations of Living SystemsMedium
A research scientist is investigating a novel enzyme involved in glycolysis. They discover that this enzyme is highly active in the presence of high AMP concentrations but is significantly inhibited by high ATP concentrations. This regulatory mechanism ensures that the enzyme's activity is adjusted according to the cell's energy status. What type of enzyme regulation is this?
- AAllosteric regulation
- BCovalent modification
- CCompetitive inhibition
- DSubstrate-level phosphorylation
Show answer & explanationAnswer & explanation
Correct answer: A. Allosteric regulation
The scenario describes a molecule (AMP/ATP) binding to the enzyme at a site distinct from the active site and altering its activity. This is the definition of allosteric regulation, where effectors modulate enzyme activity by inducing conformational changes.
Why the other options are wrong
- B. Covalent modification involves the addition or removal of chemical groups to the enzyme, which is not mentioned in the scenario.
- C. Competitive inhibition involves a molecule binding directly to the active site, which is not what's described for AMP/ATP's role in regulating overall energy status.
- D. Substrate-level phosphorylation is a mechanism of ATP synthesis, not enzyme regulation.
Allosteric Regulation
Regulation of an enzyme's activity by binding an effector molecule at a site other than the enzyme's active site, leading to a conformational change that alters its affinity for the substrate or its catalytic efficiency.
- Effector binds to an allosteric site.
- Induces a conformational change.
- Can be activation or inhibition.
- Often involves metabolic intermediates or end products.
Memory trick: Allosteric Adjuster: binds AWAY from the action, changes the whole vibe.