Three steps from UMP: two phosphates are added, then an amino group replaces the oxygen on carbon 4
Route: Uridine monophosphate → Uridine diphosphate → Uridine triphosphate → Cytidine triphosphate
UMP/CMP kinase moves a phosphate from ATP to UMP, and nucleoside diphosphate kinase adds the third. Nucleoside diphosphate kinase works on most nucleoside diphosphates and takes its phosphate from ATP in cells. CTP synthase first phosphorylates the carbon 4 oxygen of UTP with ATP, then glutamine supplies ammonia, which replaces that phosphate. Human CTP synthase assembles into filaments. UDP, made on the way, is also the start of the dTMP pathway.
Practice this pathway All pathways
| Step | Enzyme | EC | In | Out |
|---|---|---|---|---|
| 1 | UMP/CMP kinase | 2.7.4.14 | ATP | ADP |
| 2 | Nucleoside diphosphate kinase | 2.7.4.6 | ATP | ADP |
| 3 | CTP synthase | 6.3.4.2 | Glutamine, ATP, H₂O | Glutamate, ADP, Pᵢ |
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).