EXTRACTION OF ENZYMES 53 



APPROXIMATE FOOD-CONTENT OF VARIOUS PLANT-PRODUCTS 



(In percentages of the fresh weight) 



Starch. Fats. Protehis.i 



Cocoa . . 4'2 . 50*4 13-3 



Maize . . . 68*4 2 4*5 g'8 



Oat . . . 58*0 2 5'2 - io'4 



Rice . . . 75'o 0*5 9*0 



Wheat . . . 67-92 1-8 12*3 



Potato-tubers . . 20 'o o'i5 1*9 



Lettuce . . . 2*2 o'3 1*4 



Broad Bean . . 48^0 2 i'6 23*0 



Pea-nuts . . . 5'2 44^0 30*0 



In view of the great importance of enzymes in the activities 

 of the plant, the present chapter may be concluded with a brief 

 consideration of their mode of action. It should be realised 

 that such substances are probably of universal occurrence in 

 living cells. A very large number of enzymes are now known, 

 and others are continually being discovered, but only a few 

 can be mentioned here. The following table gives an epitome 

 of some of the principal enzymes found in plants : 



Enzyme. Substance acted upon. Products. 

 Diastase. Starch. Dextrin and Maltose. 

 Maltase. - Maltose. Glucose. 

 Invertase. Cane-sugar. Glucose and Fructose. 

 Inulase. Inulin. Fructose. 

 Cytase. Reserve-cellulose. Mannose and Galactose. 

 Emulsin, Myrosin, etc. Glucosides. Glucose, etc. 

 Lipases. Oils. Glycerine and Fatty Acids. 

 Proteases (proteolytic en- 

 zymes). Proteins. Peptones and Amino-acids. 

 Zymase (in Yeast, p. 256). Monosaccharides. Alcohol and Carbon Dioxide. 



The method of extraction of diastase described on p. 169 of 

 our Introduction to the Study of Plants is applicable to many 



1 In most cases the percentages given are calculated for the entire 

 nitrogenous organic matter. 



2 Total carbohydrates. 



