304 



Report of the Department of Chemistry. 



Casein. 



Paracasein 

 by rennin. 



Paracasein 

 by trypsin. 



Moisture 



Carbon in dry substance 

 Hydrogen in dry substance. . 

 Oxygen in dry substance. . . . 

 Nitrogen in dry substance. . . 

 Phosphorus in dry sybstance 

 Sulphur in dry substance. . . . 

 Ash in dry substance 



1.09 



53.50 



7.13 



*22.08 



15.80 

 0.71 

 0.72 

 0.06 



1.63 

 53.50 



7 

 *21 



26 

 94 



15.80 

 0.71 

 0.72 

 0.07 



1.27 



53.47 



7.19 



*22.04 



15.78 



0.71 



0.72 



0.09 



* By difference. 



These figures show that the composition of paracasein is the same 

 irrespective of the enzyme used to produce it. The figures also 

 show that casein and paracasein have the same percentage com- 

 position, which excludes the possibility that cleavage of any of the 

 elements of casein is a result of its transformation into paracasein 

 by enzymes. 



Harden and Macallum, in their paper, conclude that " The con- 

 version of caseinogen into casein by enzyme action is accompanied 

 by the cleavage of nitrogen, phosphorus and calcium. 11 " It seems 

 more probable to us that this cleavage follows rather than accom- 

 panies the conversion in question, and is to be attributed to a con- 

 tinuation of proteolytic activity by the enzyme beyond the point 

 where casein has been changed to paracasein. This point was 

 emphasized in my first paper on the action of rennin on casein. 12 



11 The English caseinogen is equivalent to the American casein. The English 

 casein is equivalent to the American paracasein. 



Harden and Macallum give the nitrogen-phosphorus ratio of casein as N: P = 100: 

 5.6. The high phosphorus content of their casein preparations [0.87 to 0.90 per ct.] 

 would seem to indicate the presence of considerable inorganic phosphorus. If our 

 figures are correct for the nitrogen and phosphorus content of casein [15.80 per ct. N, 

 0.71 per ct. P] the ratio would be N: P = 100: 4.50. In only one of their experiments 

 conducted to show the loss of phosphorus from the casein molecule was the N-P 

 ratio reduced to 4.50. 



12 Bosworth. N. Y. Agrl. Expt. Sta. Tech. Bull. No. 31; also Journ. Biol. Chem. 

 15:231. 



