Which enzyme links glycolysis to the TCA cycle by converting pyruvate to acetyl-CoA, and how is its activity regulated by NADH and acetyl-CoA?

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Multiple Choice

Which enzyme links glycolysis to the TCA cycle by converting pyruvate to acetyl-CoA, and how is its activity regulated by NADH and acetyl-CoA?

The enzyme that links glycolysis to the TCA cycle is the pyruvate dehydrogenase complex, which converts pyruvate into acetyl-CoA for entry into the citric acid cycle. Its activity reflects the cell’s energy state: when NADH and acetyl-CoA levels are high, the complex is inhibited. This happens because NADH and acetyl-CoA promote activation of PDH kinase, which phosphorylates and inactivates the complex, preventing more pyruvate from being turned into acetyl-CoA. When energy demand rises and NAD+ is plentiful, PDH phosphatase can activate the complex by removing the inhibitory phosphate, increasing flux into the TCA cycle.

The enzyme that links glycolysis to the TCA cycle is the pyruvate dehydrogenase complex, which converts pyruvate into acetyl-CoA for entry into the citric acid cycle. Its activity reflects the cell’s energy state: when NADH and acetyl-CoA levels are high, the complex is inhibited. This happens because NADH and acetyl-CoA promote activation of PDH kinase, which phosphorylates and inactivates the complex, preventing more pyruvate from being turned into acetyl-CoA. When energy demand rises and NAD+ is plentiful, PDH phosphatase can activate the complex by removing the inhibitory phosphate, increasing flux into the TCA cycle.

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