NUCLEIC ACIDS 



159 



but not free adeninc. The tissue contains both adenosine deaminase and 

 inosinc hydrolase but neither adenosine hydrolase nor adenase (Amberg 

 arid Jones), as indicated in the diagram: 



C 5 H 9 4 . C s II.X 4 (NH t ) C.H,X 4 (XH 2 ) 



adenosine ........ ^ adenine -t 



C 5 H 9 4 .C.,H 2 X 4 (OH) 



C 5 H,X 4 (OH) 



liypoxantlune 



111 the nuclein metabolism there are two paths to hypoxanthine, one of 

 which cannot be used by dog's liver. 



II. When an aqueous extract of pig's pancreas is allowed to digest 

 at 40 C., xanthine and hypoxanthine are formed. This was to be expected 

 because the gland contains both gnanase and adenase. But when the di- 

 gested extract is boiled with dilute mineral acid the free purines are greatly 

 increased. Guanine and additional hypoxanthine appear. 



These results can be explained in only one way. The nucleic acid 

 is first decomposed into its simple nucleotides, as was to be expected. Each 

 of the purine nucleotides is then decomposed in two ways by the action of 

 two ferments present in the gland extract. In one way, the purine base 

 is set free (action of purine nuclease), and in the other way, phosphoric 

 acid is split off leaving the nucleoside (phospho-nuclease). Thus in the 

 self -digest ion of the pancreas four purine compounds .are initially pro- 

 duced; guanine, adenine, guanine nucleoside, adenine nucleoside. 



The two free purines are deaminized and we therefore find the oxy- 

 purines among the products. The adenine nucleoside is also deaminized 

 to hypoxanthine nucleoside but the guanine nucleoside is not similarly 

 deaminized. Hence subsequent acid hydrolysis produces guanine and hypo- 

 xanthine. 



Using the terminology of yeast nucleic acid, the autolysis of pig's pan- 

 creas is expressed in the following diagram 



Nucleic Acid 



guanine 



xanthine 



guanosine adenosine 



inosine 



adenine 



hypoxanthine 



