Pathway · 5 proteins
Purine metabolism
Proteins of this group that KEGG places on its “Purine metabolism” map for Aquifex aeolicus.
How it works
This map covers the making, conversion and breakdown of purine nucleotides (A and G). The proteins on these pages include steps of purine ring building and PRPP synthesis, enzymes that remove damaged or unusual nucleotides such as dITP and XTP so they are not built into DNA or RNA, and enzymes that handle sulfate activation and polyphosphate.
Grouped by KEGG pathway map. The explanation above is the atlas’s own; the map itself covers more organisms than Aquifex.
Its proteins
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| N5-carboxyaminoimidazole ribonucleotide mutase | 5.4.99.18 | 5-carboxyamino-1-(5-phospho-D-ribosyl)imidazole + H(+) = 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate | — | 167 | Step named |
| Ribose-phosphate pyrophosphokinase | 2.7.6.1 | D-ribose 5-phosphate + ATP = 5-phospho-alpha-D-ribose 1-diphosphate + AMP + H(+) | Mg(2+), D-ribose 5-phosphate | 311 | Step named |
| dITP/XTP pyrophosphatase | 3.6.1.66 | XTP + H2O = XMP + diphosphate + H(+) | Mg(2+) | 202 | Step named |
| N5-carboxyaminoimidazole ribonucleotide synthase | 6.3.4.18 | 5-amino-1-(5-phospho-beta-D-ribosyl)imidazole + hydrogencarbonate + ATP = 5-carboxyamino-1-(5-phospho-D-ribosyl)imidazole + ADP + phosphate + 2 H(+) | — | 365 | Step named |
| 5'-nucleotidase SurE | 3.1.3.5 | a ribonucleoside 5'-phosphate + H2O = a ribonucleoside + phosphate | — | 251 | Step named |
Origins
Could purine nucleotides have lasted long enough before cells to be useful?
Joining nucleotides into chains has been demonstrated experimentally. Deamer argues that decomposition could be balanced by repeated cycles of synthesis, but agrees that further research is needed.
Purine nucleotides decompose: ester bonds hydrolyse and purines fall off the sugar, and in hydrothermal simulations below pH 3 the loss is significant (Mungi and Rajamani 2015). In the cell, five proteins in this group keep purine nucleotides supplied and converted as they are used and lost.
From the books: Deamer, Assembling Life, p. 86.
The wider question for this part of the cell: origins for making dna and rna letters.
Sources
- KEGG map aae00230 (enzymes of this organism highlighted)
Other pathways in this group: Purine biosynthesis · Pyrimidine biosynthesis · Interconversion and salvage · Deoxyribonucleotide supply · Aromatic amino acids · Pyrimidine metabolism · Histidine metabolism · Not yet placed in a pathway