4 io PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Two portions of Witte's peptone solution (500 c.c.) are placed in 

 bottles ; to one portion 100 c.c. of erepsin solution are added ; to the 

 other portion loocc. of boiled erepsin solution. To both are added 6 

 cc. of toluene and they are kept at 37 for I to 3 days. 



A portion of each is examined for proteoses and peptones by the 

 biuret reaction by adding exactly the same amount of caustic soda 

 solution (5 cc.) and exactly the same amount of I per cent, copper 

 sulphate solution. 



The solution which contained boiled enzyme will show the biuret 

 reaction (the substrate is unchanged). 



The solution which contained enzyme will either not show the 

 biuret reaction or it will be fainter than in the other solution (the 

 substrate has been hydrolysed completely or not quite completely). 



XI. Papain and Vegetable Proteoclastic Enzymes. 



Papain is prepared from the juice of the papaw tree by evaporation or by 

 precipitation with alcohol. 



Bromelin is present in the juice of the pine-apple ; the juice is neutralised 

 before testing its action. 



These enzymes can be demonstrated in a similar way to pepsin and trypsin 

 by using fibrin or coagulated egg-white as substrate : 



In six test tubes are placed : 



(1) 5 c.c. of water + 5 c.c. of papain solution + a piece of fibrin ; 



(2) 5 c.c. of water + 5 c.c. of boiled papain solution + a piece of fibrin ; 



(3) 5 c - c - f ' J N HC1 + 5 c.c. of papain solution + a piece of fibrin ; 



(4) 5 c.c. of *iN HC1 -K5 c.c. of boiled papain solution + a piece of fibrin; 



(5) 5 c.c. of 'iN Na 2 CO 3 + 5 c.c. of papain solution + a piece of fibrin ; 



(6) 5 c.c. of -iN Na 2 CO 3 + 5 c.c. of boiled papain solution + a piece of 

 fibrin ; and they are put in a water-bath at 40. 



The fibrin dissolves in (3) and (5) fairly rapidly; very slowly or not visibly 

 in (i). There is no solution in (2), (4), (6). 



Papain thus acts in the presence of either acid or alkali. 



The Products of the Action of Vegetable Proteoclastic Enzymes. 



In most respects the vegetable proteockstic enzymes resemble trypsin. 

 They form amino acids from proteins. Their action is very slow and complete 

 conversion of protein to amino acids takes several weeks. The experiment is 

 performed as described under trypsin with 100 gm. of caseinogen. 



The Presence of two Vegetable Proteoclastic Enzymes. 



By extracting seeds of Cannabis sativa with 10 per cent, salt solution and 

 acidifying the solution with acetic acid, Vines has separated the proteoclastic 

 enzymes of the plants into two groups. The precipitate contains a pepsin, the 

 filtrate an erepsin. Since other extracts can also be separated in a similar 

 manner, Vines considers that plants contain two kinds of proteoclastic enzymes : 

 (i) Peptic, producing proteoses, etc. ; (2) Ereptic, producing amino acids from 

 proteins and proteoses, etc. 



