Metabolic pathway
Purines
The purine ring is built piece by piece on top of ribose, not separately. For now the atlas covers the entry of the pathway —the activation of ribose and the step that sets the pace—; the eight steps that close the ring up to IMP are still to be written.
- In
- Ribose 5-phosphate + ATP + Glutamine + Water
- Out
- 5-Phosphoribosylamine + AMP + Glutamate + Pyrophosphate
- Location
- Cytosol
Fun facts
- PRPP synthetaseHere ATP does not give up one phosphate, but both at once. It is one of the few enzymes that transfer a whole pyrophosphate instead of splitting it.
- Glutamine-PRPP amidotransferaseUnlike pyrimidines, whose ring is assembled separately and then attached to the sugar, the purine is built piece by piece on top of ribose. This is the first brick, and the eight steps that raise the rest of the ring are still to be written in this atlas.
Reactions
| # | Enzyme | ΔG°′ |
|---|---|---|
| 1 | PRPP synthetaseEC 2.7.6.1 · irreversibleRibose 5-phosphate + ATP → PRPP + AMP | — |
| 2 | Glutamine-PRPP amidotransferaseEC 2.4.2.14 · irreversiblePRPP + Glutamine + Water → 5-Phosphoribosylamine + Glutamate + Pyrophosphate | — |
0 of 2 reactions with a documented ΔG.
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The data sheet includes the map. The logo goes at the bottom.
Sources
- Nelson, D. L. & Cox, M. M. (2021). Lehninger. Principios de bioquímica, 8.ª ed., ch. 22