788 



ADVENTURES IN RADIOISOTOPE RESEARCH 



pronounced when using freshly prepared extracts, than when old extracts 

 are applied (cf. Table 4). This observation suggests that the enzyme 

 splitting off inorganic P from nucleic acid is not identical with the enzyme 

 which is responsible for the production of organic acid-soluble compounds. 

 The presence of 2 distinct enzymes acting on polynucleotids was already 

 observed by Lehmann" — Echternacht^^^ 



The figures stated in Table 4 are thus corrected for the zero- value. 



While the mean value obtained for the ratio 



organic acid-soluble P 

 inorganic P 



= 1.5 



when applying 3 days old enzyme, this ratio declines to 0.37 when the 

 enzyme is 10 days old, and to 0.11 using 10 weeks old enzyme extracts. 



EFFECTS OF SARCOMA EXTRACTS ON LABELLED NUCLEIC ACID 



We compared the effect of enzymes extracted from the fresh tissue 

 and necrotic tissue of growing benzpyrene sarcoma and of retrograde 

 Jensen-sarcoma. As seen in Table 5, no difference of any significance is 

 shown by the 3 extracts. 



Table 5. — Effect of Sarcoma Extracts on 

 Labelled Nucleic Acid 



Time = 2l^ hours. T = 37° C. Substrate = 1 mgm 

 nucleic acid (in 2 ml) 



Sarcoma 



Percentage '^P present as 



inorganic P 



organic acid- 

 soluble P 



Growing fresh . . . 

 Growing necrotic 

 Regressive 



17 

 17 

 15 



The application of labelled substrates has especially great advantages 

 when we are faced with the problem to determine the enzymic activity 

 of very week preparations as we can restrict ourselves to the application 

 of minute amounts of substrate. 



In our experiments having only radiophosphorus samples of small 

 activity at our disposal, we had to apply P containing labelled substrates 



^1^ H. Lehmann-Echternacht, Z. Physiol. Chem. 269, 169, 187 and 201 (1941): 

 Cf. also EtriiER, Hahn and Saxuste, 8v. Vet. Akad. Arkiv f. Kemi A 24, No. 5 

 (1946). 



