ISOLATION AND COMPOSITION OF PENTOSE NUCLEIC ACIDS 



399 



TABLE V 

 Nucleotide Composition of PNA Isolated from Pancreas 



" See page 395. 

 '' Prepared in usual way. 

 '^ Ribonuclease removed prior to isolation. 

 Indirect colorimetric methods. 



TABLE VI 

 Nucleotide Composition of PNA "Cores" Resistant to Pancreatic 



Ribonuclease 



Prepa- 

 ration 



Tissue 



Aden- Guan- Cytid- 

 ylic ylic ylic 



acid acid acid 



Uridylic 

 acid Pu/Py Method" Ref. 



" See page 395. 



' Indirect colorimetric methods. 



from liver or from yeast results in the formation of pyrimidine mononucleo- 

 tides and of polynucleotides of different sizes consisting mostly of purines 

 [see Chapter 15]. The largest of these polynucleotides, the so-called "core," 

 is very rich in guanylic acid and poor in pyrimidine nucleotides (Table VI). 

 Liver PNA is thus transformed by the action of pancreatic ribonuclease 

 into polynucleotides similar in composition to pancreas PNA. It is there- 

 fore quite possible that "native" pancreas PNA is of the same composition 

 as liver PNA, but that the action of the ribonuclease converts this native 

 PNA during the isolation procedure into a degraded product of high gua- 

 nylic acid and low pyrimidine nucleotide content. 



65" S. E. Kerr, K. Seraidarian, and M. Wargon, J. Biol. Chem. 181, 773 (1949). 



