244 A TEXT-BOOK OF BOTANY. 



Cytases (cellulases) is the name applied to those enzymes 

 which are capable of dissolving cellulose. An enzyme of this 

 character is located in the aleurone layer and in the epithelium of 

 the scutellum in the germinating grain of barley. It is also found 

 in the endosperm of the date palm, the cytase being formed in 

 the embryo and the dissolved products being used up as food. 

 Enzymes of this character are also found in wood-destroying 

 fungi and bacteria. 



Proteinases (carbamases) is the name applied to those 

 enzymes which break down the true proteins or carbamide deriva- 

 tives. They are always accompanied in the plant cells by other 

 ferments, and occur especially in seeds, being more abundant in 

 those containing oil than starch, as hemp, mustard, castor oil, 

 and flaxseed. They are also found in certain fleshy fruits, as 

 figs and pineapple ; succulent leaves, as Agave, and in insectivo- 

 rous plants. In the fruit and other parts of the papaw tree (Carica 

 Papaya) occurs a proteolytic enzyme, called Papain, which readily 

 digests fibrin, thus behaving like trypsin, a ferment in the pan- 

 creatic juice. A similar ferment, called Bromelin, has been ex- 

 tracted from the fleshy pulp of the pineapple. Ferments like 

 Papain and Bromelin are naturally of very great interest, as they 

 behave like the animal ferments, pepsin and trypsin. The Papain 

 of commerce seems to be of varying composition, and unless ob- 

 tained from authentic sources is not reliable. 



Chymases or enzymes which efifect the clotting of milk. 

 The coagulating action of the fig ( Ficus Carica) was known to the 

 ancients. This action has been shown by Chodat and Rouge to 

 be due to a vegetable chymase and called by them " sykochymase." 

 A large number of plants possess the property of rendering milk 

 ropy. Of these the following may be mentioned: Ranunculus 

 bulbosus, CapscUa Bursa-pastoris, Plantago lanceolata, Mcdicago 

 lupulina, PinguicuJa vulgaris. Artichokes, etc. An enzyme of this 

 character has also been found in germinating seeds of Ricinus 

 communis, Pisum, Datura, etc., and some of the* fungi. 



Zymase, an enzyme causing the decomposition of glucose with 

 the formation of alcohol and carbon dioxide. This decomposition, 

 known as alcoholic fermentation, is considerably less simple than 

 was formerly supposed, a number of enzymes and subsidiary sub- 



