PRODUCTS OF METABOLISM 179 



Enzyme action is in no material way different from other 

 chemical reactions. The enzyme reactions are reversible and 

 consequently there is a tendency for an equilibrium to be 

 established by both sides of the equation. Enzymes act like 

 all catalytic agents, thus increasing the speed of the reaction. 

 In some cases it seems that the speed of the reaction increases 

 the amount of enzyme produced. It is not known what the 

 methods of catalysis in enzymes are. It has been noted also 

 that enzymes hasten the synthesis of some compounds. En- 

 zymes may possibly form loose chemical combinations with 

 the substances on which they act and with water, and the result- 

 ing compound be unstable and easily broken down and the 

 water remain connected with some of the components of the 

 substance which was acted upon. There is some experimen- 

 tal evidence to show that enzymes may enter into loose 

 chemical combination with the substance attacked. It has 

 also been suggested that the enzymes may increase the ioniza- 

 tion. Salt solutions favor enzyme action evidently on ac- 

 count of action of ions. 



The action of enzymes is specific. They differ from ordi- 

 nary chemical reagents in that they attack only specific 

 organic substances. For example, proteolytic enzymes only 

 attack proteins and amylolytic enzymes only carbohydrate 

 compounds. 



In some particulars enzymes are related to bacterial toxins. 

 This phase of the subject has been discussed in another 

 chapter. 



