LABELLED SUBSTRATES IN ENZYiHC PROCESSES 789 



containing 0.05 mgni P and in some cases even more. But even these 

 amounts compared favourably with the amount of substrates (1 — 2 mgm 

 P), applied in experiments using the usual chemical methods. 



In the possession of highly active radiophosphoius preparations much 

 more active substrates could be used and their weight correspondingly 

 reduced. 



Suniniary 



The authors demonstrate that labelled substrates can be applied with advan- 

 tage in enzymic studies. This is showTi by investigating the effects of blood plasma, 

 intestinal mucosa and sarcoma extracts on labelled desoxyribonucleic acid. 



The ratio of the organic acid-soluble P to inorganic P obtained from prepara- 

 tions subjected to the action of an intestinal mixcosa extract, was found to increase 

 with the age of the preparation. 



The enzyme responsible for the sphting-off of organic acid-soluble molecules 

 from desoxyribonucleic acid was found to be less stable than the enzyme responsi- 

 ble for the splitting-off of inorganic phosphate. 



