THE ACTION OF ENZYMES 71 



most important types of fermentation and the different 

 varieties of enzyme action ; those of agricultural interest 

 will be dealt with in greater detail in subsequent chapters. 

 Enzymes usually change or decompose the substances 

 upon which they act, forming from them bodies of simpler 

 constitution. The chemical reactions in the majority of 

 cases are examples of hydrolysis, a form of decomposition 

 or dissociation which involves the fixation of the elements 

 of water. One molecule of a substance is split into two 

 with the addition of water (H 2 O) : for example, under 

 the influence of the enzyme invertase, which is secreted 

 by yeast, cane sugar is split into two simpler kinds of 

 sugar, according to the following equation : 



Ci,H M O u + H 2 - C 6 H 12 6 + C 6 H 12 6 



cane sugar water glucose fructose 



A small number of ferments are known which affect the 

 oxidation of compounds ; examples of this type are the 

 vinegar plant and Bacterium aceti, which convert alcohol 

 into acetic acid. Some few ferments function as reducing 

 agents. The fibrin ferment of blood and rennin in the 

 stomach of animals bring about the coagulation or 

 " clotting " of proteins in blood and milk respectively : 

 these are termed "clotting" enzymes. 



In addition to those which effect simple hydrolysis, 

 oxidation or reduction, a large number of ferments are 

 known which induce chemical reactions of a much more 

 complicated character. Many obscure processes, such as 

 those of putrefaction and the ripening of cheese, are due 

 to the activity of ferments, but the various stages of the 

 transformations which occur are imperfectly understood. 



In naming the enzymes it is usual to add the suffix -ase 

 to the root of the name of the substance upon which the 



