What is the limiting substance in the biosynthesis of purines?
A) ribose-5-phosphate
B) 5-phosphoribosyl-β amine
C) formylglycinamidine ribonucleotide
D) 5-phosphoribosyl-α-pyrophosphate (PRPP)
E) α-D-ribose-5-phosphate

Question

Quizplus · Accepted Answer

5-phosphoribosyl-α-pyrophosphate (PRPP) is the limiting substance in the biosynthesis of purines. PRPP is formed from ribose-5-phosphate and ATP by the action of PRPP synthase. The biosynthesis of purines requires the addition of various atoms including nitrogen, carbon and oxygen from a variety of substrates. These substrates need to be activated, and the activated forms are then used for the biosynthesis of purines. It is PRPP, an activated form of ribose-5-phosphate, that is the limiting substrate for the biosynthesis of purines.

What Is the Limiting Substance in the Biosynthesis of Purines