Metabolic Pathways and Regulation · USMLE Step 1

Which enzyme in glycolysis is regulated both by allosteric effectors and by hormonal (covalent) modification in liver tissue?

  1. Hexokinase
  2. Phosphofructokinase-1
  3. Pyruvate kinase
  4. Glyceraldehyde-3-phosphate dehydrogenase
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Correct answer: Pyruvate kinase

Pyruvate kinase in the liver is allosterically activated by fructose-1,6-bisphosphate and inhibited by ATP/alanine, and is also regulated via phosphorylation by hormonal signals (e.g., glucagon) — integrating metabolic and endocrine control.

Difficulty: Medium Question 19 of 19

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