Pathway · 4 proteins
Nicotinate and nicotinamide metabolism
Proteins of this group that KEGG places on its “Nicotinate and nicotinamide metabolism” map for Aquifex aeolicus.
How it works
This map covers the making and recycling of NAD. The proteins here start the route from aspartate (L-aspartate oxidase), finish NAD using glutamine, add a phosphate to make NADP, and recycle nicotinamide released when NAD is used up, for example by the protein deacylase on this page.
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 |
|---|---|---|---|---|---|
| L-aspartate oxidase | 1.4.3.16 | L-aspartate + O2 = iminosuccinate + H2O2 | — | 510 | Step named |
| NAD kinase | 2.7.1.23 | NAD(+) + ATP = ADP + NADP(+) + H(+) | — | 274 | Step named |
| Glutamine-dependent NAD(+) synthetase | 6.3.5.1 | deamido-NAD(+) + L-glutamine + ATP + H2O = L-glutamate + AMP + diphosphate + NAD(+) + H(+) | — | 567 | Step named |
| nicotinamidase | 3.5.1.19 | — | — | 198 | Step named |
Origins
Could the nicotinamide ring of NAD have formed before cells?
Nicotinamide can be reached from plausibly prebiotic chemicals by several routes, from ethylene and ammonia (Friedmann et al. 1971) or from aspartate and dihydroxyacetone phosphate (Cleaves and Miller 2001). On this basis Yarus considers NAD-like cofactors early participants in biochemistry.
A ring is not yet a working cofactor: NAD needs ribose, phosphate and an adenine nucleotide joined in the right way, and four proteins in this group build and recycle it.
From the books: Atkins, Gesteland & Cech (eds.), RNA Worlds, p. 48; Ribas de Pouplana (ed.), The Genetic Code and the Origin of Life, p. 67.
The wider question for this part of the cell: origins for manufacturing cofactors and vitamins.
Sources
- KEGG map aae00760 (enzymes of this organism highlighted)
Other pathways in this group: Heme and quinones · Biotin and lipoate · NAD and flavins · Thiamine and pyridoxal · Folate and pterin chemistry · Lipid and cofactor connections · Coenzyme A · Aspartate-family branches · Amino-acid connections · Folate-linked carbon transfer · Serine, glycine and sulfur · Folate biosynthesis · Oxidative phosphorylation · Thiamine metabolism · Pantothenate and CoA biosynthesis · Glycine, serine and threonine metabolism · Riboflavin metabolism · Biotin metabolism · Cysteine and methionine metabolism · Porphyrin metabolism · Pyruvate metabolism · Not yet placed in a pathway