Two steps from IMP: oxidize C2, then add an amino group from glutamine
Route: Inosine monophosphate → Xanthosine monophosphate → Guanosine monophosphate
IMP dehydrogenase uses NAD⁺ to oxidize carbon 2 of the ring to a carbonyl, giving xanthosine monophosphate. This is the rate-limiting step of de novo guanine nucleotide synthesis, and the immunosuppressant mycophenolic acid blocks it. GMP synthase then activates the new carbonyl with ATP, which leaves as AMP and pyrophosphate, and replaces the oxygen with an amino group. The amino group comes from glutamine, which is hydrolyzed to ammonia; the ammonia then displaces the AMP group on the activated carbon.
Practice this pathway All pathways
| Step | Enzyme | EC | In | Out |
|---|---|---|---|---|
| 1 | IMP dehydrogenase | 1.1.1.205 | NAD⁺, H₂O | NADH |
| 2 | GMP synthase | 6.3.5.2 | Glutamine, ATP, H₂O | Glutamate, AMP, PPᵢ |
Enzyme names and EC numbers are those used on the interactive board. Checked against sources: see the claim table in the repository (tools/pathway_data/checks).