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Pyruvate Dehydrogenase Complex Regulation

The pyruvate dehydrogenase complex (PDC) links glycolysis to the TCA cycle by irreversibly converting pyruvate to acetyl-CoA. PDC regulation is a high-yield USMLE topic; deficiency causes lactic acidosis and neurological damage, making it critical for medical biochemistry and boards prep.

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What does PDC do?

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PDC (pyruvate dehydrogenase complex): Irreversibly converts pyruvate to acetyl-CoA + CO2 + NADH. Links glycolysis to the TCA cycle. Requires thiamine (B1).

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PDC activators

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PDC is activated by elevated ADP, NAD+, CoA, Ca2+, and pyruvate — signals of energy deficiency that prompt the cell to produce more acetyl-CoA for ATP generation.

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PDC inhibitors

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PDC is inhibited by elevated ATP, NADH, acetyl-CoA, and fatty acids — signals of energy excess that conserve pyruvate for gluconeogenesis.

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PDC deficiency clinical findings

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Cofactors required by PDC

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Frequently Asked Questions

What vitamins are needed for PDC activity?

PDC requires five cofactors from B vitamins: thiamine (B1), riboflavin (B2 → FAD), niacin (B3 → NAD+), pantothenate (B5 → CoA), and lipoic acid. Thiamine deficiency (e.g., in alcoholism) is the most clinically relevant cause of PDC dysfunction.

How is PDC regulated by phosphorylation?

PDC kinase phosphorylates and inactivates PDC when ATP, NADH, and acetyl-CoA are high.

PDC phosphatase dephosphorylates and activates PDC when ADP and Ca2+ are elevated.

  • Phosphorylation = inactivation
  • Dephosphorylation = activation

Why does PDC deficiency cause lactic acidosis?

When PDC is deficient, pyruvate cannot enter the TCA cycle as acetyl-CoA. Pyruvate accumulates and is shunted to lactate (via LDH) and alanine (via ALT), causing lactic acidosis. Neurological damage results from impaired ATP production in the brain.