322 JOHN M. BUCHANAN 



to Eq. (22). It can be seen that the driving force for inosinic acid biosyn- 

 thesis according to Eq. (22) is derived, in effect, from the hydrolysis of 9 

 equivalents of ATP (including 2 equivalents required for glutamine forma- 

 tion and 2 equivalents for formate activation). Suggestions have been made 

 in preliminary form to explain the formation of carbon to nitrogen bonds 

 by a coordinated attack on a carbon atom (such as a carboxyl carbon) by 

 the nucleophilic nitrogen donor, and by the electrophilic nucleoside tri- 

 phosphates. Further studies along these lines should crystallize our present 

 tentative concepts of how phosphate compounds are integrally involved in 

 the synthesis of a variety of carbon to nitrogen bonds not only in purine 

 reactions but in the synthesis of other nitrogen-containing compounds. 



