Photolysis and hydrolysis of adenosine 5'-phosphates

Mild acid hydrolysis of adenosine 5'-di, tri- and tetra-phosphate (ADP, ATP and ADTP) occurs predominantly in the side chain, yielding orthophosphate and adenosine 5'-mono-phosphate (AMP). Photolysis results in breaking of the 5'-C-O-P bond, yielding orthophosphate for AMP and mainly condensed phosphates for ADP, ATP and ADTP, together with decomposition products of adenosine. The photolytic breaking of the 5'-C-O-P bond is not enhanced by excitation of the strongly absorbing adenine ring followed by energy transfer but results from direct excitation of the very weakly absorbing ribosephosphate-moiety of the molecule. The arguments for this are: (i) cyclic adenosine 3'5'-mono-phosphate, which is sterically hindered for direct energy transfer from the adenine ring to the phosphate-ester bond, is photolyzed at approximately the same rate as AMP, and (ii) the rate of disappearance of the strong absorption band due to the adenine ring is higher than the rate of liberation of orthophosphate. (author)