Biochemistry · Molecule
Hypoxanthine !
Hypoxanthine is a purine the cell can either recycle (HGPRT) or break down to uric acid (xanthine oxidase).
Updated 2026-11-01
Loading the 3D model…
Key facts
- It is formed from inosine by purine nucleoside phosphorylase.
- Crossroads: HGPRT + PRPP → IMP (salvage) or xanthine oxidase → xanthine (breakdown).
- Allopurinol is an isomer of hypoxanthine (one nitrogen moves position).
- It is the base of IMP and inosine.
- Formula
- C₅H₄N₄O
- PubChem
- CID 135398638
Structure
- A purine with an oxo group at C6 (6-oxopurine).
Clinical notes
- On allopurinol, hypoxanthine and xanthine accumulate; together they are more soluble than uric acid alone.
- It rises in xanthinuria and in HGPRT deficiency.
Pathways
Related conditions
Related
- Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
- Xanthine oxidase
- IMP (inosine monophosphate)
- Uric acid
- Adenosine deaminase (ADA)
Test yourself
Think of the answer, then tap the question to see it.
What are the two fates of hypoxanthine?
Salvage to IMP by HGPRT, or breakdown to xanthine and uric acid by xanthine oxidase.
Which drug is an isomer of hypoxanthine?
Allopurinol, which inhibits xanthine oxidase.
Which enzyme releases hypoxanthine from inosine?
Purine nucleoside phosphorylase (PNP), using phosphate.
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: Hypoxanthine (CID 135398638) (PubChem, NCBI, 2026) · Public domain; Purine salvage (Reactome, 2026); Purine catabolism (Reactome, 2026).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.