Anaplerosis and gluconeogenesis — The mitochondrial conversion of pyruvate to oxaloacetate (OAA) by pyruvate carboxylase has which of the following features?

Introduction:
Pyruvate carboxylase catalyzes the ATP-dependent carboxylation of pyruvate to oxaloacetate, providing an anaplerotic entry to the TCA cycle and the first committed step of gluconeogenesis. This question reviews the essential requirements and localization of this reaction.

Given Data / Assumptions:

• Pyruvate carboxylase is a biotin-dependent enzyme.
• CO2 (as bicarbonate, HCO3−) is incorporated into pyruvate to form oxaloacetate.
• The reaction occurs in the mitochondrial matrix and is activated by acetyl-CoA.

Concept / Approach:
Confirm the cofactor (biotin), the chemistry (carboxylation/fixation of CO2), and subcellular localization (mitochondria). If all statements are true, the comprehensive answer is “All of the above.”

Step-by-Step Solution:

Verification / Alternative check:
Biotin deficiency impairs anaplerosis/gluconeogenesis; mitochondrial isolation studies locate pyruvate carboxylase activity in the matrix.

Why Other Options Are Wrong:

Common Pitfalls:
Forgetting acetyl-CoA is an allosteric activator; confusing cytosolic PEPCK with mitochondrial pyruvate carboxylase localization.

Final Answer:
All of the above.