CHEMISTRY OF NUCLEOSIDES AND NUCLEOTIDES 



179 



a. Adenosine Di- and Triphosphate (ADP and ATP) 



These two substances participate in the reversible phosphorylation of a 

 very large number of important intermediates in metabolic processes. ATP 

 is usually isolated from muscle2i2-2i4 q^ after enzymic synthesis from adeno- 

 sine.2i* Two of its three phosphate groups are removed by acid hydrolysis, 

 the other products being adenine and ribose-5-phosphate. In alkali it gives 

 adenosine-5'-pho&phate and pyrophosphoric acid.^'^ Titration with alkali 

 indicates the presence of three primary and one secondary phosphate acidic 

 groups, suggesting a linear triphosphate. Positions 2' and 3' are unsubsti- 

 tuted since ATP increases the conductivity of boric acid and consumes 1 

 mol. periodate.2i^ These observations indicate the structure XL. 



O — 



OH OH OH OH 



L-CH-CH-CH-CH-CHrO-P-O-P-OH 



I II II 



N. -N 



NH. 





XLI 



Adenosine diphosphate 



-O- 



OH OH OH OH OH 



l-CH-CH-CH-CH-CH^-O-P-O-P-O-P-OH 



N. .N 







NHj 



N' 



XL 



Adenosine triphosphate 



ADP (XLI) may be prepared by enzymic dephosphorylation of ATP^'s. 219 

 with the loss of one phosphate group. The presence of a pyrophosphate 

 residue is supported by titration, and the formulas of both these coenzymes 

 have been confirmed by synthesis. 



212 K. Lohmann, Naturwissenschaften 17, 624 (1929). 



213 C. H. Fiske and Y. Subbarow, Science 70, 381 (1929). 

 21* G. A. LePage, Biochem. Preparations 1, 5 (1949). 



216 p. Ostern, T. Baranowski, and J. Terszakowec, Z. physiol. Chem. 251, 258 (1938). 



216 K. Lohmann, Biochem. Z. 233, 460 (1931). 



217 B. Lythgoe and A. R. Todd, Nature 155, 695 (1945). 



218 K. Lohmann, Biochem. Z. 282, 104 (1935). 



219 K. Lohmann, Biochem,. Z. 282, 120 (1935). 



