CLASSIFICATION 459 



to the nature of enzymes ; are all these different ferments 

 really specific, or are there only a few enzyme-nuclei which, 

 before they can attack any particular substance, have to have 

 attached to them certain molecular complexes according to 

 the nature of the substrate ? 



There may, in certain cases, be made out a curious associa- 

 tion of different enzymes. Thus Vines * found that when a 

 tissue gave the guaiacum reaction, with or without the addition 

 of peroxide, that same tissue also exhibited proteolytic activity 

 and vice versa. Thus in the fruit of the orange, neither the 

 juice nor the pulp gives the guaiacum reaction, whilst, on the 

 other hand, the peel does. The peel is actively proteolytic, 

 but not the pulp and juice. Similarly the latex of the fig, 

 papaw, lettuce, and spurge, has proteolytic qualities and also 

 gives the peroxidase reaction. The meaning of this associa- 

 tion is not clear. 



CLASSIFICATION OF ENZYMES. 

 The following classification of enzymes, based on the 

 chemical reactions in which they exert their accelerating 

 influence, indicates the extensive use made by nature of these 

 catalysts : — • 



I. Hydrolytic Enzymes. 



(a) Ester or fat-splitting enzymes (esterases) : Lipase, chlorophyllase. 



(b) Carbohydrate-splitting enzymes (carbohydrases) : — ■ 



Invertase, which hydrolyses cane sugar to dextrose and levulose. 



,, ,, ,, raffinose to levulose and melibiose. 



Maltase „ ,, maltose (malt-sugar) to dextrose. 



Lactase ,, ,, lactose (milk-sugar) to dextrose and 



galactose. 

 Amylase or Diastase, which hydrolyses starch to maltose and 



dextrin. 

 Inulase, which hydrolyses inulin to levulose. 

 Pectinase, which hydrolyses pectins to arabinose and galactose. 

 Cytase, which hydrolyses hemicellulose to mannose, galactose, etc. 

 (c) Glucoside-splitting enzymes : — 



Emulsin, which hydrolyses amygdalin to glucose, hydrocyanic 



acid and benzaldehyde. 

 /3-methylglucoside to glucose and 

 methyl alcohol. 

 Myrosin ,, ,, potassium myronate to allylisothio- 



cyanate, glucose, and potassium 

 hydrogen sulphate. 

 Phytase „ ,, phytin to inosite and phosphoric acid. 



* Vines : " Ann. Bot.," 1903, 17, 257. 



