Biochemistry · Enzyme
Pyruvate carboxylase !
Pyruvate carboxylase turns pyruvate into oxaloacetate inside the mitochondrion: the first step in making glucose and in topping up the Krebs cycle.
Updated 2026-11-01
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Key facts
- Pyruvate + CO₂ + ATP → oxaloacetate + ADP + Pi; it uses biotin (B7) to carry the CO₂.
- Acetyl-CoA is its obligatory activator: with plenty of acetyl-CoA, pyruvate goes to oxaloacetate rather than to PDH.
- It is the main anaplerotic reaction: it replenishes Krebs-cycle oxaloacetate.
- Mitochondrial; oxaloacetate leaves for the cytosol as malate (or aspartate) to continue gluconeogenesis.
Regulation
- Allosteric activator: acetyl-CoA.
- Glucagon and glucocorticoids increase the amount in the liver.
Inhibitors and toxins
- Avidin (raw egg white): traps biotin
- Biotinidase or holocarboxylase synthetase deficiency (no active biotin)
Clinical notes
- Pyruvate carboxylase deficiency (PC gene) causes lactic acidosis, hypoglycaemia and developmental delay; the neonatal form is very severe.
- In biotin deficiency all carboxylases fail (pyruvate, propionyl-CoA, acetyl-CoA and methylcrotonyl-CoA carboxylases): dermatitis, hair loss and acidosis.
Pathways
Related conditions
Related
- Pyruvate
- Acetyl-CoA
- Phosphoenolpyruvate carboxykinase (PEPCK)
- Krebs cycle (citric acid cycle)
- Pyruvate dehydrogenase complex (PDH)
- ATP (adenosine triphosphate)
Test yourself
Think of the answer, then tap the question to see it.
Which vitamin does pyruvate carboxylase need?
Biotin (B7), which carries activated CO₂ to pyruvate.
Which molecule activates pyruvate carboxylase and what does it mean?
Acetyl-CoA: it signals spare fatty acids and the need for oxaloacetate, for glucose or for the Krebs cycle.
Why can eating a lot of raw egg white cause biotin deficiency?
Avidin in raw egg white binds biotin and prevents its absorption; cooking denatures it.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: PC: Pyruvate carboxylase, mitochondrial (human) (UniProt, 2026); PC gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Pyruvate carboxylase deficiency: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); 3BG3: Crystal Structure of Human Pyruvate Carboxylase (missing the biotin carboxylase domain at the N-terminus) (RCSB Protein Data Bank, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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Representative model, for educational purposes only.