PHOSPHORUS FROM CASEINOGEN. 447 



In the second experiment the total P.XX, was estimated before adding 

 the trypsin. There was an insoluble residue containing 4 mgm. P 2 O 5) 

 which could not therefore be derived from the trypsin ; the amount 

 obtainable in a 50 c.c. sample was less than 1 mgm., since the 50 c.c. 

 of the 2 per cent, solutions of trypsin only contained 8 mgm. P 2 O 3 . 



Again, in our experiments on the digestion of casein by 1 per cent, 

 caustic soda, a similar insoluble residue containing phosphorus was left, 

 so that the residue of a caseinogen -trypsin digestion is derived partly 

 from the trypsin and partly from the caseinogen. 



Trypsin, in the manner usually prepared, contains nucleo-proteid or 

 its decomposition products. Nucleo-proteid is digested with difficulty 

 by trypsin, and leaves a residue containing phosphorus. We have 

 investigated the action of trypsin on yeast-nuclein (Merck) with regard 

 to the rate of separation of soluble P 2 O S and soluble nitrogen in order to 

 determine to what extent it was dissolved by trypsin : 



N 



10 gm. yeast-nuclein dissolved in 40 c.c. -% NaOH for solution and 500 c.c. of water : 

 1 gm. trypsin added. 



Soluble P 2 S Soluble N 



Time in mgm. in grs. 



19-5 0-0392 



1 hour 23-1 0-0553 

 3 hours 24-8 0-0700 

 8 26-4 0-0868 



24 29-4 0-1008 



2 days 32-5 0-1078 



Soluble P 2 O 5 Soluble N 



Time in mgm. in grs. 



3 days 33-2 0-1155 



6 35-2 0-1162 



10 38-3 0-1218 



15 41-1 0-1078 



21 40-1 0-1022 



Total 49-5 0-1666 



The yeast-nuclein was therefore digested by trypsin, but not 

 completely, a residue containing one-fifth of the total P. 2 O 5 and about 

 three-fourths of the total nitrogen being left in the precipitate by tannic 

 acid. After 10 days the amount of soluble nitrogen decreased, but we 

 have not determined whether any synthetical action had occurred. 



From the small quantity of indigestible residue left by caseinogen 

 when it is digested by trypsin or by alkali, it seems extremely probable 

 that this is present as impurity and is of the nature of nucleo-proteid. 

 Traces of nucleo-proteid might be expected in milk, as a result of the 

 disintegration of the secreting cells of the mammary glands. 



The conclusions which can be drawn from these experiments are, 

 (1) that the whole of the phosphorus of caseinogen is converted into 

 a soluble form (i.e. is not precipitated by tannic acid) by the action 

 of trypsin ; (2) that the small insoluble residue is derived from nucleo- 

 proteid which is contained partly in the caseinogen as impurity and 

 partly in the trypsin. 



