12 



Me7idel and Underhill — Papa'in-digestion. 



tones. The latter were removed by precipitation with an equal volume of Lugol's 

 solution saturated with ammonitim sulphate. This peptone precipitate could 

 always be divided into two fractions, one insoluble (V) and the other soluble 

 (VI) in 95 per cent, alcohol. These portions both gave the biuret reaction. 



Experiment B. This was carried out under precisely the same conditions as 

 Experiment A, except that 2.2 liters of 0.02 per cent. HCl were added instead of 

 the alkali. A total of 8 grams of papain A was added, and the digestion stopped 

 after 28 days. No leucin, tyrosin or tryptophan were found. The results of the 

 fractional analysis are given below. 



Expeynment C. Alkaline digestion containing 300 grams of freshly precipi- 

 tated casein, 1500 c.c. of 0.25 per cent. NasCOs, 4 grams of papain B and thymol 

 solution. Digestion at 38° C. for 26 days. 



Experiment D. Acid digestion like Experiment C except that 1500 c.c. of 

 0.02 per cent. HCl were added in place of the alkali. 



Experiment E. Alkaline digestion like Experiment C, the enzyme used being 

 papain C. Digestion at 38° C. for 26 days. 



Experiment F. Acid digestion like Experiment D, with papain C. Digested 

 at 38' C. for 26 days. 



A summary of the results of the fractional precipitation of the 

 digestion products according to the general plan outlined under 

 Experiment A follows. The iigures given indicate cubic centimetres 

 of saturated sulphate solution in a total volume of ten cubic centimetres. 



FRA.CTIONAL ANALYSIS OF THE PAPAIN DIGESTION. 



The results obtained with different enzyme preparations and under 

 varying conditions show a fairly close agreement with one another 

 and a resemblance to those already published by Alexander for the 

 gastric digestion of casein. He concluded that at least four caseoses 

 and two casein-peptones are formed in the pepsin-hydrochloric acid 

 proteolysis of casein. Our results indicate that similar products may 

 arise through the action of papain, and they lend additional emphasis 

 to the specific character of papain as an enzyme. 



^ Alexander : Zeitschrift fiir physiologische Chemie, 1898, xxv, p. 418. 



