No, I don’t see the problem. You just need a little to make a lot. If this weren’t the case then life would be impossible. Each of us started out as a single cell, and if we couldn’t make more ATP then we couldn’t get past a few hundred thousands cells.
Conversely, the “problem” you see is dependent on no other pathways existing in the history of life, so you run into the same problem.
It can be derived from diet or from breakdown of NAD. ATP is neither nictonamide or NAD. NADP is not NAD, so the de novo pathway is not autocatalytic. On top of that, NAD/P only act as proton donors which could easily be filled by other molecules. Once you have a biosynthesis pathway for a proton donor it isn’t hard to see why it could replace the activity of other proton donors. The same for phosphate donors.
@T_aquaticus Your answer is sort of along the lines of what I expected. 1. Diet 2.Alternate pathway replaced. I have a hard time with “NAD is not NADP” so their appearance together in the same pathway I find a little problematic. And here’s the other thing. ATP contributes way more that phosphate groups.
Here’s another gnarly cofactor, coA. The last 5 steps in its biosynthesis are highly conserved, from bacteria to mammals, and all but one require ATP. But not just for phosphate.
I don’t have access to the pdf to show you the figure directly. Here is a You tube that lays out the pathway is excruciatingly slow detail. https://www.youtube.com/watch?v=KQSbyhxtW-oPantothenate plus 4 ATP plus cysteine = CoA, except one of those ATPs contributes AMP, not just phosphate. ATP features prominently in a lot of cofactors.
Now here’s where it get’s interesting. And I really want to hear people’s responses to this. I have pointed you the universal path to CoA from pantothenate (Vitamin B5) depends on ATP. Now obviously, we get pantothenate from our diet and from bacteria in our gut. I have not yet looked up the plant pathway so I can say how they make pantothenate, but in bacteria it requires another two cofactors, THF and surprise, NADPH (E coli, reference
It’s easy to say, all you need is an electron donor and a phosphate donor, an electron acceptor, a carboxyl carrier. But have a look at the structures of these gnarly cofactors. There is some serious shifting of charge going on. You would think it could have been done much more parsimoniously, and without the labyrinthine cross-referencing biosynthetic pathways (though maybe not, if they all require the same kinds of chemistry)!
Does anyone have suggestions for how biosynthesis might have been bootstrapped without these cofactors? Especially ATP, which is absolutely critical to so many functions in the cell?
One proposal I came across recently suggested acetyl thioesthers:
Goldford JE, Hartman H, Smith TF, Segrè D. Remnants of an Ancient Metabolism
without Phosphate. Cell. 2017 Mar 9;168(6):1126-1134.e9. DOI: 10.1016/j.cell.2017.02.001