Evolutionary history of ATP

I’ve recently been trying to learn some of the fundamentals of biochemistry (especially of phosphate bond energy) and I’ve run across something in my studies. Adenosine Triphosphate, the primary energy currency of life, seems ideal for its role (it has medium energy as far as organophosphorus bonds are concerned, triphosphate bond increases Gibbs energy, among others). Here’s my questions: What was the first use of ATP in life? Was it in metabolism or as a nucleic acid construction molecule?I ask this question primarily due to my unfamiliarity with biochemistry literature, in the hopes that someone who has studied biochemistry extensively will say, Oh that’s easy. We were told in class So far in my research this does not seem to be the case (and my online googling brings up a bunch of creationist nonsense- like Trueorigin).From my investigation so far, and using a bit of logic, I think that ATP was first used as a nucleic acid construction molecule. Why? A few reasons:1) It’s complex. It has a sugar (fairly oxidized organic compound) bound to an adenine (reduced H-C-N molecule) with a triphosphate attached to the sugar. These three separate molecules likely form in different environments. If ATP had an ancient, metabolism first origin, it would be very hard to prebiotically synthesize. However, if it was used as a nucleic acid building block first, then this problem would be part of the whole how did the RNA world first develop which more researchers are working on.2) It has properties specifically selected for as a nucleic acid building block. First and foremost, the stereochemistry of ribose is specified for the formation of long nucleic acid chains. The stereochemistry of ribose is not utilized to this extent in metabolism. Also, ATP is used to build nucleic acid via the reaction:
ATP + NA --> A-NA + PPi
where PPi is pyrophosphate, P2O74-.
Release of pyrophosphate is an energetically favorable reaction as pyrophosphate is a rare component of cellular systems. Typically ATP in metabolism releases energy via loss of a phosphate bond:
ATP --> ADP + Pi
where Pi is orthophosphate. This reaction is much more dependent on product concentrations than the prior reaction, as orthophosphate is much more abundant than pyrophosphate.So in my opinion, ATP was first used as a building block for RNA, but due to its energetic versatility, it was coopted into metabolism. This does establish some history for life’s early evolution:RNA-dominated replication
Followed by
ATP as energy currency
Followed by
DNA-dominated replicationThoughts? Comments?

Thread moved here from the Proposed New Topics forum.

Nobody knows.There was once a camp of scientists that believed that life started twice.The first kind of life was metabolism and the other was replication.Somehow these two forms of life evolved at different times at different places and somehow they came together.ATP, ADP, AMP, GMP, GDP, GTP, CTP, CDP, CMP could have all been doing different things all at the same time from the very beginning, but like I said, no one knows.All the nucleosides can be phosphorylated and they all do different things.You'll find that most biomolecules that perform some function are simply analogs to other biomolecules that perform yet another function. This is about as plausible as any hypothetical scenario that anyone has dreamt up so far.

Fair enough, and that's the conclusion I was starting to reach.Quick question- does the adenine (or other nucleobase) actually serve much of any purpose in metabolism? It seems that a sugar di- or polyphosphate (glucose, ribose) could act just as well as an activated nucleotide.

I really don't think anyone knows what ATP was originally used for, but your hypothesis is probably as good as any. I've never really delved into the early life theories, since I'm not sure how much proof you have for any scenario. I do like the self-catalytic network concept though.It is exactly this sort of multifunctional use of molecules in biochemistry that showed me the inherant beauty of life at a molecular level. Like how many of the intermediates in the Kreb's cycle are very easily converted into amino acids, and amino acids funneled back into the Kreb's cycle. Its all about moving both molecules and energy around. It certainly made learning all those metabolic pathways a bit easier

ATP synthesis is via a proton gradient, which as a minimum requirement needs a membrane. most abiogenesis proposes a replicator created earlier say on a clay particle or evaporated pool.so off the top of my head i'd propose that its first use was probably in some kind of replicator synthtesis (1 strand-rna or dna) then later after simple membranes form then ATP synthesis can be explored.

I'm just getting to that part in the biochemistry text I'm reading (Lehninger's 1975 text- pretty old, but on sale at a used bookstore).Any good biochemistry text suggestions?

1975 is ancient history in biology, though biochemical pathways were probably mostly characterised by them. My old textbook was Biochemistry by Stryer. Molecular Cell Biology by Lodish et al. is probably a better all round textbook however. Not so much emphasis on biochemical pathways though.