Amadeus believes that the high purine content of meat is toxic.  I have
found that purine-rich foods are absolutely essential to my health; if I
don't eat dark meat for breakfast, my energy level suffers.  Has anyone else
noticed a difference between the effects of light and dark meat on his or
her health?  Dr. George Watson and Dr. Rudolf Wiley both believed that the
people who thrived on a meat-rich diet also needed plenty of purines for
efficient energy production and a balanced metabolism.  (Conversely, the
patients who fared best on a high-carb diet needed to restrict their purine
intake.)

At any rate, here is some of the information I've found on purines.  The
following excerpt is from Dorit, R.L. et al., _Zoology_, Saunders College
Publishing, 1991, p. 49:

<<*Nitrogenous Bases as Energy and Signaling Molecules*

Finally, the nucleosides adenosine and, on occasion, guanosine [formed from
adenine and guanine, respectively, both purines], may play more than one
crucial role in living systems.  As we have seen above, these nucleosides
are components of DNA.  But the triphosphate forms of adenosine and
guanosine, adenosine triphosphate (ATP) and guanosine triphosphate (GTP),
are also the energy molecules of the cell.  Precisely because the bonds
connecting phosphates are so energy rich, they can be synthesized to store
the energy of the exergonic (energy requiring) metabolic reactions.  Cells
take in sugars and other high-energy compounds, but the energy is not
available to power the metabolic activity of the cell until it is changed to
ATP or GTP.

And there are yet more functions: the monophosphate form of adenosine,
adenosine monophosphate (AMP), undergoes a slight chemical modification to
become a major "signal molecule" in the cell, mediating the action of
several important hormones.  Finally, nucleosides can also form part of
larger molecules, coenzymes, that facilitate the catalytic action of
enzymes.  These multiple roles reflect a common evolutionary phenomenon, in
which a molecule that may have been present early in cellular evolution has
been drafted into a variety of different roles.>>