66 



BIOLOGICAL CHEMISTRY 



required for most of these substances. The enzyme which 

 hydrolyses starch and glycogen does not hydrolyse the other 

 substances. Different enzymes are required for each of 

 maltose, lactose and cane sugar. 



A careful examination of the various substances acted on 

 by enzymes shows a definite relation between the structural 

 formulae of the substances attacked by the same enzyme. 

 The analogy has been made that the enzyme fits the substrate 

 like a key fits a lock,* or as a hand fits a glove. t 



One example will suffice. The glucosides can be divided 

 into two groups, according to whether they have an a or ft 

 configuration (p. n). 



The enzymes that hydrolyse the a forms will not attack the 

 ft forms and the converse.} 



TABLE XI. 



Relations of Enzyme to Substrate 



Glucoside. 



d-Methyl-^-Glucoside 

 p-Methyl-^-Glucoside 

 a -Methyl- /-Glucoside 

 /3-Methyl-/-Glucoside 

 a-Ethyl-d-Glucoside 

 /3-Ethyl-d-Glucoside 

 /3-Phenol-d-Glucoside 

 a-Methyl-d-Galactoside . 

 0-Methyl-tf-Galactoside . 

 Methyl-d-Mannoside 

 Methyl-/-Mannoside 

 a-Methyl-/-Xyloside 

 -Methyl-/-Xyloside 

 Methyl-/- Arabinoside 

 Methyl rhamnoside 

 Methyl glucopeptoside . 



A similar relation is found between the nature of the amino 

 acid linkages in protein and the enzymes that loosen these 

 linkages. 



The specific relationship of enzymes is frequently used for 

 analytical purposes, and examples will be given later (see 

 p. 182). 



MODE OF ACTION OF ENZYMES 



There are two views as to the manner in which enzymes 

 produce acceleration of the reaction. One is that the enzyme 



* E. Fischer, Ber., 1894, vo1 - 2 7 P- 2992. 



t E. F. Armstrong, The Simple Carbohydrates and the Glucosides, 

 p. 80. 



J E. F. Armstrong, The Simple Carbohydrates and the Glucosides. 

 Longmans, 1912, p. 79. 



