Four steps: remove the phosphate, remove the ribose, remove the amino group, then oxidize
Route: Guanosine monophosphate → Guanosine → Guanine → Xanthine → Uric acid
A 5'-nucleotidase removes the phosphate from GMP to give guanosine. Purine nucleoside phosphorylase cleaves the bond to ribose with phosphate rather than water, which gives the free base guanine and ribose 1-phosphate. Guanine deaminase adds water and releases ammonium, which gives xanthine. Xanthine oxidoreductase oxidizes xanthine to uric acid, the same last step as in the adenine route. Guanine can also return to GMP through the salvage pathway.
Practice this pathway All pathways
| Step | Enzyme | EC | In | Out |
|---|---|---|---|---|
| 1 | Cytosolic purine 5'-nucleotidase | 3.1.3.5 | H₂O | Pᵢ |
| 2 | Purine nucleoside phosphorylase | 2.4.2.1 | Pᵢ | Ribose 1-phosphate |
| 3 | Guanine deaminase | 3.5.4.3 | H₂O | NH₄⁺ |
| 4 | Xanthine oxidoreductase | 1.17.3.2 | O₂, H₂O | H₂O₂ |
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).