432 CHEMICAL DYNAMICS 



the solution of the casein-products, give a voluminous precipitate 

 which remains permanent for many weeks. 



The fact that paranuclein A, rather than paranuclein or casein, 

 is produced in the reversion of protein hydrolysis which pre- 

 sumably occurs in the experiments described above, is probably 

 to be interpreted as follows : 



In the initial stages of the hydrolysis of casein, paranuclein 

 is produced, part of which undergoes further hydrolysis and 

 part of which escapes further hydrolysis owing to the fact that 

 it is thrown out of the sphere of action of the enzymes by pre- 

 cipitation (59) (60) (61). The proportion of the paranuclein 

 which undergoes hydrolysis passes through the intermediate 

 stage paranuclein A and then to the stage of proteoses and 

 peptones. Only that proportion of the paranuclein which under- 

 goes this further hydrolysis, therefore, yields to the filtered and 

 concentrated digest all of the substances which are necessary 

 for resynthesis. In event of synthesis occurring in a mixture 

 such as that described above, the first substance which resulted 

 which is insoluble in solutions of weak acids would necessarily 

 be thrown out of the sphere of action and the reaction would 

 terminate at this point. Hence, from what has been said above, 

 it is evident that were a member of the paranuclein group pro- 

 duced in these mixtures it would be paranuclein A, rather than 

 one of the other members of the group of higher phosphorus- 

 content. 



In the above experiments, in order to secure synthesis of the 

 paranuclein, the products of its hydrolysis had to be concen- 

 trated to a considerable degree. From what has been said in 

 the beginning of this section the rationale of this procedure will 

 be evident. Later experiments, however (53), showed that 

 previous concentration of the products of the complete peptic 

 hydrolysis of paranuclein is not necessary if the synthesis be 

 carried out in the presence of a considerable excess of pepsin 

 and at a much higher temperature, namely from 60 to 70 de- 

 grees. 



I made up the following mixtures in duplicate, having first 

 ascertained that the unconcentrated products of the peptic 

 hydrolysis of AT/50 alkali caseinates and 10 per cent pepsin 

 (Gruebler's puriss. sice.) can be kept separately for weeks at 

 65 degrees without a trace of precipitate forming in either solution. 



