154 PKOTEINS AND AMINO- ACIDS [ch. 



incubate at 38° C, tryptophane can be readily detected after a day or 

 two. This has been found to be true for the tissues of many seeds^ 

 seedlings, roots, stems, leaves and fruits (such as those already mentioned 

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

 type of enzyme. The detection of this enzyme is facilitated by the 

 addition of the artificial supply of peptone. 



Expt. 144. The detection of erepsins in plants. 



(a) In resting seeds. Grind up 10 gms. of seeds in a coffee-mill, and add 100 c.c. 

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

 following seeds may be used : Hemp {Cannabis sativa\ Castor-oil {Ricinus communis)^ 

 Pea {Pisum sativum), Scarlet Runner {Phaseolus multifiorus\ Broad Bean {Vicia 

 Faha) and fruit of Wheat ( Triticum vulgare). Test for tryptophane. Controls should 

 be made in these and the following cases. 



(6) 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 {Carica 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. 



^ Is prepared from fibrin and consists of a mixture of proteoses and peptone. It is free 

 from tryptophane. 



