Question 6 of 16
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The major control of de novo pyrimidine nucleotide synthesis in man is:
- A. feedback inhibition of glutamine-PRPP amidotransferase.
- B. feedback inhibition of aspartate transcarbamylase.<
- C. availability of N-acetyl glutamate.
- D. substrate availability.
- E. competitive inhibition of carbamoyl phosphate synthetase II.
The correct answer is (E).
Comments:
- A. This is the control for purine nucleotide synthesis.
- B. This is true in bacteria but not in man.
- C. This is the control of CPS I which leads to urea synthesis but NAG is not an activator of CPS II.
- D. Although this is true for some pathways, eg. degradation of purines, it is not true for this one.
- E. Correct. UTP is competitive with ATP in this reaction.
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cna
Last modified 1/5/95