There are 4 purines and 4pyrimidines that are of concern to us.
Purine and pyrimidine metabolism.
We have previously developed a method to selectively incorporate 13C, 15N into the purine bases via a total enzymatic synthesis of ATP and GTP starting from serine, glucose, NH4+ and CO2 with up to 66% isolated yield . Historically, labeled UTP and CTP have been prepared from chemically synthesized bases. For example, chemical synthesis of 15N3 uracil from (15NH4)2SO4 is very efficient giving up to 75% yield . An efficient chemoenzymatic synthesis of U-13C, 15N-UTP has also been demonstrated starting from U-15N, 13C-uracil and U-13C-glucose giving an isolated yield of 60% . Specifically labeled 13C2′, 15N1,3- uridine has been synthesized from K13CN and 15N-urea with overall yields of 6.1% and 35.2% based on respective starting materials . A chemical synthesis of 13C6-UTP from K13CN was also achieved with an overall yield of 24%. Specifically 15N-labeled cytidine has been chemically synthesized from uridine and 15NH4Cl with yields of 94% for 15Namino- cytidine, 72% for 15N3-cytidine, and 62% for 15Namino, 3 - cytidine . Specifically deuterated CDP has been chemically synthesized from tert-butyldimethylsilyl cytidine derivatives with ~17% overall yield for both 2H2′ and 2H3′ labels . Here we report a total enzymatic synthesis of UTP and CTP through the expansion of our current enzymatic methods to the de novo pyrimidine biosynthetic pathway. The result is an efficient flexible method to incorporate 15N, 13C, and 2H into both the base and ribose moieties of pyrimidine nucleotides.
PURINE AND PYRIMIDINE SYNTHESIS PART 1.
You have frequently heard ATP referred to as the "universal energycurrency" of the cell, and this is true for all organisms. Why ATP ended upbeing such a pivotal coenzyme, and not GTP, UTP, etc., is probably just a matterof chance. The free energy of biological oxidation reactions can be stored inthe bonds of ATP (chemical energy). It's relatively easy to hydrolyzepyrophosphate linkages in ATP, with the result that a considerable amount offree energy is released (Go' = -30.5kJ/mol for ATP hydrolysis to ADP and Pi ).If this were released intothe cell as heat, it would serve no useful purpose as far as making anendergonic chemical reaction proceed, since there's no way for the cell totransduce heat energy into work. But, if two reactions are "coupled"such that the product of an endergonic reaction is the reactant of an exergonicone (and the magnitude of the free energy change of the exergonic one is greaterthan that of the endergonic) then the exergonic reaction pulls the endergonicone through an intermediate. In other words, for chemical energy to be socoupled, there must be an intermediate common to both reactions in the set.