374 ENZYMES 



ammonium sulphate by dialysis. The solution of enzyme thus 

 purified may be dried at a temperature below 50 C. 



Vines * separated peptase from ereptase by making use of 

 the fact that the former is hardly soluble in water but readily 

 so in a dilute solution of sodium chloride, whilst ereptase is 

 easily soluble in water. The material, e.g. seed of Cannabis 

 sativa, is ground and extracted with a 10 per cent solution of 

 sodium chloride. The solution is filtered and rendered just 

 acid by the addition of acetic acid, whereby a white precipitate 

 of protein is formed, which is filtered off. The acid filtrate 

 has marked proteolytic qualities but has no action on fibrin ; 

 it therefore contains the ereptase. The fibrin-digesting pro- 

 tease (peptase) is in the precipitate ; to recover it, wash the 

 precipitate with a 10 per cent solution of sodium chloride 

 slightly acidified with acetic acid. The precipitate is next 

 treated with distilled water and filtered ; the filtrate, which 

 has an opalescent appearance, digests fibrin but has no effect 

 on Witte peptone. In order to ensure the best results, the 

 temperature should be kept as low as possible during filtration. 



GENERAL CONSIDERATIONS. 



According to Vines, the proteases of plants fall into two 

 main groups, peptase and ereptase. Peptase hydrolyses pro- 

 teins to albumose or peptone, but does not act on albumose 

 or peptone whether produced by its own digestion of protein 

 or added in the form of Witte peptone.f Ereptase hydrolyses 

 proteins, albumoses and peptones to amino acids, such as leu- 

 cine and tyrosine. Peptase dissolves readily in a saline solu- 

 tion but is hardly soluble in water, whilst ereptase is easily 

 soluble in water. Both may occur in a plant, e.g. the seeds of 

 Cannabis sativa,^ the latex of Carica papaya the enzyme of 

 which is termed papai'n yeast, etc. In fact the mixture is, 

 or was, commonly termed vegetable trypsin. On the other 

 hand, some plants which exhibit proteoclastic properties only 

 have peptase. This is, however, seemingly very rare ; Dro- 

 sera provides an example. II 



* Vines: "Ann. Bot.," 1908, 22, 103. 



f Vines: id., 1905, 19, 171; 1908, 22, 103. 



Vines: id., 1908, 22, 103. 



Vines: id., 1909, 23, i. 



|| White : " Proc. Roy. Soc., Lond.," B., 19 to, 83, 134. 



