Laser Raman spectroscopy as a mechanistic probe of the phosphate transfer from adenosine triphosphate in a model...

Laser Raman spectroscopy has been used to study a phosphate transfer reaction from ATP to Pi or arsenate in dimethyl sulfoxide. The spectra support a mechanism involving Mg-2+ binding to the alpha or beta phosphates of ATP leaving the third phosphate free for the transfer reaction. The data also indicate the formation of a relatively stable intermediate which is facilitated by the presence of dimethyl sulfoxide and a dicarboxylic acid (maleate). The intermediate has a Raman spectrum with a band at 1090.5 cm- minus 1 similar to the end product ADP, but is formed much more rapidly. Since the model reaction has many features in common (e.g., activation by maleate) with the transfer reactions catalyzed by coupling factors from spinach chloroplast, Raman spectroscopy may also prove to be a useful tool in the elucidation of biological energy transfer reactions.