All of the following are true concerning the regulation of the purine biosynthetic pathway EXCEPT:
A) ATP is the energy source for AMP synthesis.
B) ADP and GDP are feedback inhibitors of ribose-5-phosphate pyrophosphokinase.
C) "A" and "C" nucleotides allosterically inhibit glutamine phosphoribosyl pyrophosphate amidotransferase (Gln:PRPP amidotransferase).
D) The rate of IMP formation is dependent on the levels of the adenine and guanine nucleotides produced.
E) PRPP competitively inhibits the enzyme Gln:PRPP amidotransferase.

Question

Quizplus · Accepted Answer

E) PRPP is actually a substrate for the enzyme Gln:PRPP amidotransferase, not a competitive inhibitor. This enzyme catalyzes the first committed step in purine nucleotide biosynthesis, where PRPP is converted to 5-phosphoribosylamine, using glutamine as a nitrogen source.

All of the Following Are True Concerning the Regulation of the Purine