IMP (inosine monophosphate) !

IMP is the first complete purine the cell makes; AMP and GMP come from it.

Updated 2026-11-01

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Key facts

End product of de novo purine synthesis and branch point towards AMP and GMP.
Its base is hypoxanthine; it also forms by salvage (HGPRT) and by AMP deamination.
IMP → AMP needs GTP and aspartate; IMP → GMP needs NAD⁺, glutamine and ATP.
It feeds back to inhibit PRPP amidotransferase.

6-Mercaptopurine is activated to thio-IMP, which mimics IMP and blocks several pathway enzymes.
In hard-working muscle, AMP is deaminated to IMP (purine nucleotide cycle).

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What is the base of IMP?

Hypoxanthine.

Which energy source does each branch from IMP use?

The AMP branch uses GTP and the GMP branch uses ATP, so each purine promotes the synthesis of the other.

Why is IMP called a branch point?

Because it is the common product of de novo synthesis and from it the cell decides to make AMP or GMP.

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: Inosinic Acid (CID 135398640) (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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Representative model, for educational purposes only.