Question

The pyruvate carboxylase catalyzed conversion of pyruvate to oxaloacetate is a(an)

• A. Anaplerotic reaction
• B. Cataplerotic reaction
• C. Elimination reaction
• D. Hydrolytic reaction

Hint:

Remember that "anaplerotic" means "filling up." Pyruvate carboxylase is the most important anaplerotic enzyme in animal tissues and is activated by acetyl-CoA.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Anaplerotic reactions are chemical reactions that replenish intermediates of a metabolic pathway, such as the Citric Acid Cycle (TCA cycle), which are continuously withdrawn for various biosynthetic pathways.

Step 2: Detailed Explanation:
The TCA cycle functions as both a catabolic and anabolic (amphibolic) pathway.
Intermediates like oxaloacetate are regularly drained from the cycle to synthesize amino acids and other biomolecules.
To keep the cycle running efficiently, these intermediates must be replenished.
Pyruvate carboxylase catalyzes the ATP-dependent carboxylation of pyruvate to form oxaloacetate:
\[ \text{Pyruvate} + \text{HCO}_3^- + \text{ATP} \xrightarrow{\text{Pyruvate Carboxylase}} \text{Oxaloacetate} + \text{ADP} + \text{P}_i \]
This reaction directly refills the oxaloacetate pool of the TCA cycle, making it a classic example of an anaplerotic ("filling up") reaction.

Step 3: Final Answer:
The reaction is classified as an Anaplerotic reaction.