Biochemistry · Molecule
PRPP (phosphoribosyl pyrophosphate) !
PRPP is activated ribose: the starting point for making and recycling every nucleotide.
Updated 2026-11-01
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Key facts
- It is made from ribose-5-phosphate and ATP by PRPP synthetase.
- It is used by de novo purine synthesis (committed step), pyrimidine synthesis (UMP synthase), base salvage (HGPRT, APRT) and NAD⁺ synthesis.
- Its concentration controls purine synthesis: more PRPP, more amidotransferase activity.
- It rises in HGPRT deficiency and in PRPP synthetase superactivity: both cause hyperuricaemia.
- Also called
- 5-Phosphoribosyl-1-pyrophosphate
- Formula
- C₅H₁₃O₁₄P₃
- PubChem
- CID 7339
Structure
- A ribofuranose ring with a phosphate on C5 and an α-pyrophosphate on C1.
- When a base attaches, the pyrophosphate leaves and the bond ends up β, as in nucleotides.
Clinical notes
- In Lesch-Nyhan syndrome PRPP unused by HGPRT accumulates in red cells and speeds purine synthesis.
- Hydrolysis of the released pyrophosphate makes PRPP-using reactions irreversible.
Pathways
Related conditions
Related
- PRPP synthetase
- Glutamine-PRPP amidotransferase
- Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
- Adenine phosphoribosyltransferase (APRT)
- UMP synthase
- NAD⁺ (nicotinamide adenine dinucleotide)
Test yourself
Think of the answer, then tap the question to see it.
Which enzyme makes PRPP, and from what?
PRPP synthetase, from ribose-5-phosphate and ATP (which is left as AMP).
Why does PRPP rise in HGPRT deficiency?
HGPRT is a major PRPP consumer; without it PRPP is left over and stimulates de novo purine synthesis.
How does PRPP use differ between purines and pyrimidines?
In purines the ring is built on PRPP; in pyrimidines the finished ring (orotate) is attached to PRPP.
Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Phosphoribosyl Pyrophosphate (CID 7339) (PubChem, NCBI, 2026) · Public domain; Purine ribonucleoside monophosphate biosynthesis (Reactome, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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