Which one of the following pairs correctly matches the enzyme with its allosteric activator?

Correct option is D

​

Allosteric activators are molecules that bind to an enzyme at a site other than the active site, increasing its activity. Let's analyze each option:

1. Phosphofructokinase (PFK) : Citrate → Incorrect

   • Citrate is an allosteric inhibitor, not an activator. PFK is activated by AMP and Fructose-2,6-bisphosphate.

2. Pyruvate dehydrogenase : NADH → Incorrect

   • NADH is an inhibitor, not an activator, of pyruvate dehydrogenase. The enzyme is activated by Ca²⁺ and AMP.

3. Pyruvate carboxylase : ADP → Incorrect

   • ADP inhibits pyruvate carboxylase. The enzyme is activated by Acetyl-CoA.

4. Pyruvate kinase : Fructose-1,6-bisphosphate → Correct

   • Pyruvate kinase is allosterically activated by Fructose-1,6-bisphosphate, which is an example of feed-forward activation in glycolysis.

Information Booster

1. Allosteric Regulation: Many enzymes have regulatory sites where molecules bind to either activate or inhibit the enzyme.
2. Phosphofructokinase (PFK-1): A key enzyme in glycolysis, activated by AMP and Fructose-2,6-bisphosphate, but inhibited by ATP and Citrate.
3. Pyruvate Dehydrogenase Complex (PDC): Converts pyruvate into Acetyl-CoA; activated by Ca²⁺ in muscle cells and inhibited by NADH and Acetyl-CoA.
4. Pyruvate Carboxylase: A key enzyme in gluconeogenesis; activated by Acetyl-CoA, signaling a need for glucose synthesis.
5. Pyruvate Kinase Activation: Pyruvate kinase is activated by Fructose-1,6-bisphosphate, ensuring that glycolysis continues efficiently.
6. Feed-Forward Activation: This mechanism ensures that once glycolysis starts, it proceeds efficiently to the final step.
7. Energy Regulation: These regulatory mechanisms help maintain energy balance in cells by controlling glycolysis and gluconeogenesis.