PROTEASES 373 



example.* The seeds of this plant contain much protein which 

 undergoes proteolysis before translocation takes place. But 

 no enzyme has been discovered in the seed which is capable 

 of digesting these proteins ; ereptase, however, which can 

 hydrolyse the proteases derived from the digestion of these 

 seed proteins, is abundant. Dean considers that the proto- 

 plasm plays the part of a peptase, whilst the ereptase may 

 carry the digestion further. 



The plant proteases are less rigid than the corresponding 

 ones from animal sources in respect to their activity in acid or 

 alkaline media. Thus the proteolytic enzyme of Drosera is 

 active in acid, alkaline or neutral media ; papam is active both 

 in acid and alkaline media, thus differing from animal pepsin ;-|- 

 and some proteases will only work provided the reaction be 

 acid, e.g., Nepenthes, malt, mushroom and yeast.;|: The 

 natural reaction of the plant juice is the best to maintain for 

 general experiments. 



TRYPTOPHANE REACTION. 



The presence of tryptophane is an indication of the activity 

 of trypsin-like proteolytic ferments. Tryptophane may occur 

 naturally in the sap of the plant, its presence being associated 

 with the ripening of fruits and the germination of protein-con- 

 taining seeds.§ 



In order to ascertain whether the enzyme be a tryptic one, 

 a solution of it, or some of the more or less crude plant-extract, 

 is added to a solution of peptone and placed in an incubator 

 for some time, according to the strength of the solutions, kept 

 at a temperature of 40^ A little toluol may be added as an 

 antiseptic. To test, a few drops of the liquid are placed in a 

 watch glass, acidified with acetic acid, and then a little chlorine 

 water is added. The appearance of a marked yellow to pink 

 coloration indicates the presence of tryptophane. If performed 

 on a large scale, the liquid may be finally shaken up with 

 amyl alcohol which dissolves the pink chlorine compound and 

 eventually rises to the top. It may be separated by means 

 of a small separating funnel and spectroscopically examined. 



*Dean : loc. cit. t Mendel: "Am. Journ. Med. Sci.," igoz. 



:t Vines: "Ann. Bot.," 1905, 19, 171. 



§ Vines: id., 1902, 16, i; 1903, 17, 237, 597. 



