158 S. S. COHEN 







/ II II 



acetate (CHgC— OH) + ATP ^ adenyl acetate (adenosine— O—P—O—C—CHs) + PP 



I 

 OH 



butyrate + ATP ^ adenyl butyrate + PP 



L-leucine + ATP ^ adenyl leucine + PP 



O 



II II 



sulfate + ATP ^ adenyl sulfate (adenosine— 0—P—O—S— OH) + PP 



I II 



OH O 



O 



II II 



carbonate + ATP ^ adenyl carbonate (adenosine — — P — — C — OH) + PP 



I 

 OH 



In many of these cases, the active coenzyme of a reaction system is a 

 further phosphorylated derivative of these metabohtes, as produced in the 

 reactions: 



DPN-kinase 



DPN + ATP > 2-phospho-DPN (TPN) + ADP 



kinase 



dephosphocoenzjone A + ATP >■ S-phosphocoenzjone A (CoA) + ADP 



kinase 



adenyl sulfate + ATP > 3'-phospho 5'-phosphosulfatoadenosine (active 



sulfate) + ADP 



In other instances, the adenyl anhydride is a precursor to the formation 

 of the immediate metabohte, as in the reactions in which the acyl moiety is 

 transferred from phosphoanhydride to form the reactive thioester. 

 adenyl acetate + coenzyme A ^ AMP + acetyl-coenzyme A 

 adenyl butyrate + coenzjTne A ^ AMP + butyryl-coenzjmie A 



The ready reversibility of some of the reactions Hsted above attests to the 

 high group-transfer potential of the activated compounds involved, i.e., 

 they are designated as high-energy compounds.^ 



We can note that the reactions described for acetate and butyrate con- 

 stitute the probable mechanisms of their in vivo activation in preparation for 

 various acetylations and acyl transfers. These wiU be summarized below, as 

 will the subsequent reactions of compounds such as UDPG, CDP choline, 

 active sulfate, adenyl carbonate, and adenyl leucine (leucine adenylate). 



^ Gulick (1955) has suggested that life originated under conditions in which phos- 

 phorus was only partially oxidized, permitting the formation of compounds such as 

 guanidine phosphite. Dehydrogenation in this instance might then lead to the formation 

 of a high energy compound, phosphoguanidine, formally analogous to the phosphagens, 

 phosphocreatine, and phosphoarginjne. 



