Name this molecule. You must be specific. We need the exact name and why it's important in every living cell.
The molecule is N-carboxyaminoimidazole ribonucleotide. Three people, "dunbar," Steve LaBonne, and "Martin S." got the right answer. N-carboxyaminoimidazole ribonucleotide is an essential intermediate in the pathway to purine synthesis in most cells. Purines are needed to make DNA and RNA. See below the fold to find out if you need this molecule ....
The relevant part of the pathway begins with aminoimidazole ribonucleotide (AIR). It is converted to N-carboxyaminoimidazole ribonucleotide in a CO2 (in the form of bicarbonate) fixing reaction that requires ATP. In the second step, the carboxylate group is shifted from the nitrogen atom to the carbon atom in the ring forming carboxyaminoimidazole ribonucleotide (CAIR). The newly added carbon atom will become C-6 of the completed purine ring.
In prokaryote, these two steps are catalyzed by separate enzymes. In eukaryotes, the two enzymes have become fused to form a single large multifunctional enzyme that can carry out both steps. In vertebrates, it is thought that a single enzyme (AIR carboxylase) can transfer bicarbonate directly to create CAIR. This conclusion is based on a single 1994 paper that studied the chicken enzyme. As far as I know it hasn't been confirmed.
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N-Carboxyaminoimidazole riboucleotide, i.e. the intermediate between aminoimidazole ribonucleotide and carboxyaminoimidazole ribonucleotide in the synthesis of purine nucleotides.
Back to studying!
This stumped me for a while because textbooks tend to show the AIR carboxylase reaction as taking AIR directly to CAIR without showing this intermediate, NAIR. (I have a dim recollection that that is how it actually does work in vertebrates and only in vertebrates- is that correct?) Knowing Larry the opportunity to point out this textbook omission / vertebrate-centrism is no doubt precisely why he chose this molecule. ;)
This intermediate (NAIR) only occurs in bacteria and fungi. 'Higher' eukaryotes use AIR carboxylase to go direct from AIR to CAIR. The only other thing to note is that this is the de novo synthesis path for the purines and nothing cellular goes very far without AMP or GMP. As far as I know nothing survives without this pathway except possibly the obligate intracellular parasite families Chlamydia and Rickettsia. Chlamydia acquires ATP from its host cell for metabolic activity and is metabolically inert in the infectious "elementary body" part of its developmental cycle. However, I don't know if they produce purines for use in DNA synthesis or rely on salvage pathways.
Chlamydia has two parts to its developmental cycle. The infectious extracellular phase I have mentioned and, secondly, the metabolically active, replicating phase during which the bacterium is inside a host cell. A bacterium in the latter phase is called a reticular body when observed microscopically. I hope this clarifies my above comment.
Cheers.
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