CLASSIFICATION OF FERMENTS 205 



II. Ferments which break up biose sugars into simpler sugars. 

 Invertase attacks cane-sugar, changing it into equal quantities of 



glucose and fructose. 

 Maltase changes maltose into d-glucose. 

 Lactase decomposes lactose or milk sugar, changing it into glucose 



and galactose. 



Others are raffinase, trehalase, and melizitase, which decompose 

 respectively the sugars raffinose, trehalose, and melecitose. 



III. Ferments which split up glucosides, giving rise to glucose and 

 various other substances. The best known are : 



Emulsin, which decomposes the glucoside amygdalin into glucose, 

 . benzaldehyde, and hydrocyanic acid. It can also decompose 



the glucosides arbutin, salicin, and helicin. 

 Myosin changes potassium myronate into glucose, potassium 



hydrogen sulphate, and essential oil of mustard. 

 Others are tannase, erythrozyme, and rhamnase. 



IV. The proteoly tic ferments which decompose albuminous substances. 

 Pepsin is found chiefly in the stomachs of the higher animals. In 



vegetable tissues its occurrence is doubtful. It splits up albuminous 

 substances into peptones and albumoses. 



Trypsin carries the decomposition much further. The first products 

 are probably the same as for pepsin, but the final products are 

 ammonia, amido acids, and di-amido acids, which are relatively simple 

 bodies of known constitutions. Trypsin is more widely distributed as 

 well as more energetic than pepsin, and is found in many animals and 

 plants. 



Galactase. Found in milk, the proteids of which it hydrolyses, 

 carrying the decomposition to the extent of the liberation of ammonia. 



Papain. Found in the fruit of the papaw tree. It decomposes 

 proteids, and in its action is intermediate between pepsin and trypsin. 



V. The fat-splitting ferment (Lipase). Changes fats into fatty 

 acids and glycerine. This ferment is found in all mammalian animals, 

 the chief seat of its formation being the pancreas. It is also fairly 

 widely distributed among the lower animals. In the vegetable kingdom 

 it occurs in the seeds of plants which store fat as a reserve material, 

 e.g. castor oil plant. 



VI. The clotting ferments. The result of their action is the forma- 

 tion of a semi-gelatinous clot, which subsequently shrinks and becomes 

 semi-fibrous. 



Rennet. Found in the pancreas of many animals, in various insec- 

 tivorous plants, in fruits, and other parts of plants. When it is added 



