VIII] THE PROTEINS AND PROTEASES 189 



above and others) ; the result indicates the wide distribution of an 

 erepsin type of enzyme. The detection of this enzyme is fiicilitatcd 

 by the addition of the artificial supply of peptone. 



Expt. 138. The detection of e.repsins in plants. 



(a) In resting seeds. Grind up lOgms. of seeds in a coffee-mill, and add 100 c.c. 

 of water, 0-2 gm. of Witte's j^eptone and a little toluol. Incubate for 2-3 days. The 

 following seeds may be used : Hemp {Cannabis sativa), Castor-oil {liieinus comnumis), 

 Pea {Pisum sativum), Scarlet Runner {Phaseolits midtifloriis), Broad Bean ( Vicia 

 Faba) and fruit of Wheat {Triticum vidgare). Test for tryptophane. Controls 

 should be made in these and the following cases. 



{b) In germinating seeds. Take 10 germinating peas, pound in a mortar, add 

 100 c.c. of distilled water, 0'2 gm. of Witte's peptone, and a little toluol. Incubate 

 for 3 days. Test for tryptophane. 



(c) In leaves. Pound up a small cabbage leaf, add 100 c.c. of water, 0-2 gm. of 

 Witte's peptone and a little toluol. Incubate for 3 days. Test for tryptophane. 



{d) In roots. Pound up about 20 gms. of fresh carrot root. Add about 100 c.c. of 

 water, 0"2 gm. of Witte's peptone and a little toluol. Incubate for 3 days. Test for 

 tryptophane. 



The pepsin type of enzyme is less readily detected. It has long 

 been known that the pitchers of the Pitcher-plant {Nepenthes) secrete 

 an enzyme which digests fibrin. A few other cases of protein-digesting 

 enzymes are well known, such as the so-called " bromelin " from the fruit 

 of the Pine-apple {Ananas sativus), "cradein " from the latex and fruit of 

 the Fig {Ficus) and " papain " from the fruit and leaves of the Papaw 

 Tree {Garica Papaya). Such enzymes were formerly termed "vegetable 

 trypsins" as they were thought to be of the type of animal trypsin which, 

 alone, hydrolyzes proteins to amino-acids. On analogy with the results of 

 research with other enzymes, it seems likely that " papain," " cradein " 

 and " bromelin " are all mixtures of pepsin and erepsin. In addition to 

 these better known cases, it has also been stated that fibrin is digested 

 by extracts or pounded pulp of the fruits of the Cucumber and the 

 Melon, the " germ " (embryo) of Wheat, the bulbs of Tulip and Hyacinth, 

 the seedlings of the Bean, Pea, Scarlet Runner, Lupin and Maize, and 

 the ungerminated seeds of the Pea, Lupin and Maize. These have also 

 been shown to contain erepsin. 



A separation of pepsin from erepsin has been achieved in the case 

 of the seeds of the Hemp {Cannabis sativa) by means of the different 

 solubilities of the two enzymes in water and salt solutions. 



Expt. 139. The extraction and the separation of the two enzymes, erepsin and 

 pepsi7i, from Hemp-seed {Cannnhis sativa) (Vines, 22). Weigh out 50gms. of hemp-seed, 

 grind it in a coffee-mill and extract with 2.50 c.c. of 10 'Vo sodium chloride solution. 



