URIC ACID AND THE PURINE BODIES 671 



this connection it is interesting to note that much evidence is accumulat- 

 ing to show that the respiratory functions of cells are linked up with 

 the presence in the cytoplasm of bodies called mitochondria composed of 

 phospholipin and protein. (Lynch. 61 ) 



The History of Nucleic Acid in the Animal Body. We shall first 

 of all study the manner in which nucleic acid may be broken down. As 

 is to be expected from its complex structure, various types of enzymes 

 are concerned in this process. The first to act are known as the nucle- 

 ases. They split the tetranucleotide molecule into two dinucleotides, 

 which immediately afterward split further into mononucleotides. Four 

 nucleotides, two of purine and two of pyrimidine, are thus formed from 

 each molecule of nucleic acid. Each nucleotide molecule may now un- 

 dergo decomposition in one of two ways: (1) either by the splitting off 

 of phosphoric acid, leaving a nucleoside (guanosine or adenosine), or 

 (2) by the splitting off of both phosphoric acid and carbohydrate, leaving 

 free purine bases. Nucleases have been found which specifically effect 

 either of these decompositions, and they have been called phospho- 

 nucleases* (1), and purine-nucleases (2), respectively. In the decompo- 

 sition of nucleic acid all of the four purine compounds guanine, guano- 

 sine, adenosine and adenine may be formed. This is illustrated in the 

 accompanying schema, in which the nucleic acid is represented as a 

 purine nucleotide: 



Nucleic^Acid (without the pyrimidine group) 

 """V 



- - V / \~x v / 



/ (Action of nucleates) \ 



Guanine f-(7) Guanosine Adenosine (8)- Adenine 



<*) (5) (6) 



(Actioni of deaminizing enzymes) 



v v 



Xanthosiije Inosine 



(9) (Action of hydrolyzing enzymes) (10) 



UrfcAcidf-(ll) Xanthine < (11)- >Hypwanthine 



(Action of xanthine oxidase) 



(Jones.) 



The next step in the disintegration process is that the amino group 

 is removed and the corresponding oxypurine is produced. To bring this 

 about, there exists a specific deaminizing enzyme for each of the above 

 amino compounds, and each enzyme is named according to the exact 

 amino purine upon which it acts; thus, guanase (3), guanosine-deaminase 

 (4), adenosine-deaminase (5), and adenase (6) have all been identified. 



. 



"The numbers refer to the enzymes indicated in the schema. 



