X, A, 1 



Pratt: Papain 



21 



age of protein digested by 25 milligrams of papain is almost 

 exactly half that found with 50 milligrams at corresponding 

 points on the curves. In all cases, the mineral acid was neutral- 

 ized by an equivalent amount of sodium hydroxide solution im- 

 mediately before precipitating with copper sulphate and acetic 

 acid. Otherwise, milky solutions are encountered that will not 

 permit filtration. 



The peculiar transition point in these curves was thought to 

 indicate the appearance of uncombined hydrochloric acid, but 

 such is not the case. A similar series was prepared for the 

 purpose of determining free acid by titration, using Topfer's 

 reagent (dimethylamidoazobenzol) as indicator. None of the 

 flasks showed the presence of free acid. The milk in the flasks 

 containing 0.02 per cent acid was not coagulated, that with 

 0.04 and 0.06 per cent showed slight coagulation, while the re- 

 mainder was coagulated. 



In as much as the enzyme solution had been added after acidifi- 

 cation, there was a possibility that the papain acted only as the 

 surface of curds thus formed and that the results, therefore, did 

 not represent the true rate of digestion. This possibility was 

 avoided by adding the enzyme solution to the milk and water 

 before acidifying. All the solutions were maintained at 0° to 

 prevent digestion before the addition of acid. It was impossible 

 to start the digestions as promptly in this manner as in previous 

 cases. The time, therefore, was extended to ninety minutes to 

 compensate for irregularity at the beginning and to insure equi- 

 librium. Papain 6 was used. The results are found in Table 

 XVIII. 



Table XVIIL- 



-Papain digestion of 



inilk protein 



in acid 



solution. 



No. of 

 flask. 



Milk. 



Water. 



Papain 

 solution. 



Papain. 



Hydro- 

 chloric 



acid 

 solution. 



Hydro- 

 chloric 

 acid. 



Protein 

 undi- 

 gested. 



Protein 



di- 

 gested. 



Protein 



di- 

 gested. 



Parts of 

 protein 

 digested 

 by 1 part 

 papain. 





cc. 



cc. 



cc. 



mg. 



cc. 



Per cent. 



mg. 



mg. 



Percent. 





1 



26 



15 



10 



50 







0.00 



620 



522 



45.7 



110.4 



2 



25 



14 



10 



50 



1 



0.02 



617 



525 



46.0 



10.5 



3 



25 



13 



10 



50 



2 



0.04 



640 



502 



44.0 



0.0 



4 



25 



12 



10 



50 



3 



0.06 



687 



455 



39.8 



9.1 



5 



25 



11 



10 



50 



4 



0.08 



747 



395 



34.5 



7.9 



6 



25 



10 



10 



50 



5 



0.10 



820 



322 



28. 2 



6.4 



7 



25 



9 



10 



50 



6 



0.12 



937 



205 



18.0 



4.1 



8 



25 



8 



10 



50 



7 



0.14 



987 



155 



13.6 



3.1 



9 



25 



7 



10 



50 



8 



0.16 



982 



160 



14.0 



3.2 



10 



25 



6 



10 



50 



9 



0.18 



1.001 



141 



12.4 



2.8 



H 



25 



5 



10 



50 



10 



0.20 



1,005 



137 



12.0 



2.7 



Protein in blank = 1,142 milligrams. 



