RECENT WORK ON PROTEIN-HYDROLYSIS 441 



able to attribute the inhibition of the peptoclastic power to the 

 presence of the salt, and to postulate that sodium fluoride can 

 inhibit the action of erepsin but not that of pepsin. 



This means of discrimination did not, however, go further 

 than papain, which was thus shown to be probably a mixture. 

 Vines adopted, consequently, another method, which was the 

 study of various solvents to extract the enzymes from the 

 same material. He was at once successful with yeast and 

 with the mushroom. With these materials he found that a 

 rapidly prepared watery extract could not digest fibrin, but 

 could split up Witte peptone. Using a salt solution extract 

 prepared equally rapidly, fibrin was digested in twenty-four hours, 

 and W r itte peptone was equally easily decomposed. Evidently 

 the first enzyme, provisionally regarded as a pepsin, is not 

 soluble in distilled water, but dissolves in salt solution, while 

 the second, an erepsin, is soluble in both. 



Further power of differentiation between them was afforded 

 by varying the reaction of the digesting liquid. In his early 

 work on the same two fungi, Vines found that peptolysis and 

 fibrin digestion were affected in much the same manner, but not 

 to the same degree, by the reaction, whether acid, alkaline, or 

 neutral. He subsequently applied this method to bromelin, 

 nepenthin, and the proteases obtained from germinating barley 

 and from the bulb of the hyacinth. Certain precautions were found 

 necessary ; the acid and alkali used had to be added in due 

 proportion to the concentration of the enzyme in the digesting 

 liquid. The acid employed was hydrochloric, and the alkali 

 carbonate of sodium. The antiseptic used was not always the 

 same, but was always that which previous experience had 

 shown to affect the decompositions as little as possible. 



In the case of papain it was found that fibrin digestion was 

 not materially affected by difference of reaction, taking place 

 equally well in presence of 0-5 per cent, or 1 per cent, of sodium 

 carbonate, and of o'2 per cent, or 0-3 per cent, of hydrochloric 

 acid, hydrocyanic acid being the antiseptic ; on the other hand, 

 the splitting of the peptone was diminished in alkaline liquids. In 

 neutral solution the fibrin was digested more readily than the 

 peptone. The experiments were in all cases made in pairs, the 

 fibrin and the peptone being subjected to the papain in separate 

 vessels simultaneously and side by side. 



Vines concludes that papain contains a fibrin-digesting 



