Distribution of the Enzymes
The enzymes responsible for the disruption of the nucleic acid complex are not to be found in all the body tissues. Moreover, the distribution of the enzymes in the various organs and tissues varies in different species of animals. Of the various organs the liver, spleen, thymus, and pancreas more particularly contain enzymes in abundance. As to their varied location in different animals, it may be noted that the enzyme responsible for the oxidation of xanthine into uric acid, viz., xanthine-oxidase, is found in man only in the liver. In other animals, also, it is of localised distribution, being as a rule only found in the liver or in the liver and kidney. The dog, however, appears to be an exception, xanthine-oxidase being found in a variety of its tissues.
Adenase, the deaminising enzyme, is not to be found in any organs in man. Neither does it exist in any of the tissues of the rat. Consequently, if adenine be injected subcutaneously in rats, it undergoes oxidation, without abstraction of its amino group.
On the other hand, guanase, also a deaminising enzyme, is in man to be detected in the kidney, lung, and liver, but not in the pancreas or spleen. In the pig, however, guanase is lacking, and its absence no doubt explains why deposits of guanine may occur in the muscles constituting the so-called guanine gout met with in swine. It is worthy of note also that in pigs’ urine the content of purin bases exceeds that of uric acid.
To sum up, in man the enzyme, xanthine-oxidase, which forms uric acid from xanthine, is located chiefly or exclusively in the liver. This, of course, represents the final stage of purin metabolism, but the antecedent chemical processes involved in the disruption of nucleic acids are initiated by the action of enzymes in the intestinal juices and wall, and to a consideration seriatim of these changes we now proceed.