Which pattern of regulation correctly describes human PRPP glutamyl amidotransferase, the committed enzyme of de novo purine synthesis?
- A Inhibited only by the end product uric acid
- B Activated by AMP and GMP, inhibited by PRPP
- C Inhibited by AMP and GMP, activated by high PRPP ✓
- D Regulated solely by covalent phosphorylation by protein kinase A
Correct answer: C. Inhibited by AMP and GMP, activated by high PRPP
Explanation
PRPP glutamyl amidotransferase is feedback-inhibited by the purine end products AMP and GMP, acting synergistically at separate sites, and is driven forward when intracellular PRPP rises. Uric acid is a catabolic end product and does not regulate this enzyme. Covalent modification is not the regulatory mechanism here.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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