LABELLED SUBSTRATES IN ENZYMIC PROCESSES 



787 



perature lor 2 days. The liquid obtained after filtration through cloth 

 and addition of toluene was stored in an ice-box. 



The non-split nucleic acid present in the solution after treatment with 

 intestinal enzyme is precipitated with cold trichloracetic acid. The 

 precipitation is much facilitated by simultaneous precipitation of pro- 

 teins. We found it very convenient to add blood plasma to the enzyme 

 extract containing the radioactive substrate, previous addition of 

 trichloraccetic acid. As we base all our determinations on radioactive 

 measurements, the presence of phosphorus compounds in the plasma 

 does not interfere with our determinations of the inorganic P and total 

 organic acid-soluble P split off from the labelled nucleic acid added. 



As in the experiments with blood plasma, described above, the intes- 

 tinal mucosa extracts not only split off inorganic P from nucleic acid but 

 also organic acid-soluble phosphorus compounds, which are presum- 

 ably a mixture of nucleotids of a low degree of polymerization. The 

 appearance of organic acid-soluble phosphorus compounds is more 



Table 4. — Effect of Intestinal Mttcosa 

 Extract on Labelled Nttcleic Acid 



Temperature 37''C. Amount of substrate in 

 sample = 0.70; 3.6; 1.2: 1.1 mgm 



50* 



