It will be seen that the disintegration of nucleic acid involves many stages, and its complexity is such that we make no apology for drawing upon the masterly monograph of Walter Jones for further elucidation of this intricate question. In relating the history of nucleic acid in the animal body Jones has found it convenient to introduce certain terms wherewith to designate the various elements of the nucleic acid molecule. Thus, the molecule in its entirety is termed a tetra-nucleotide. The cleavage of this complex is initiated by the action of two specific enzymes. Through their agency the tetra-nucleotide is first cloven into two di-nucleotides, which immediately divide up into four mono-nucleotides. These ferments are:—
(1) Phospho-nuclease (which splits off the phosphoric acid radicle, leaving a nucleoside, guanosine or adenosine).
(2) Purin-nuclease (which splits off the purin radicle, viz., separates out both phosphoric acid and carbohydrate groups, leaving free purin bases).
Now, in sequence to either of the foregoing cleavages by the phospho- or purin-nucleases another set of enzymes come into the field. Under their deaminising effect the amino group is abstracted, with the formation of either free oxy-purins or oxy-purins still bound in glucoside-like combination with sugar.
If the oxy-purins are free, the following is the reaction:—
Should, however, the guanine glucoside be present:—