60 THE NATURE OF LIFE 



in this way is called a catalyzer. There 

 are catalyzers which hasten oxidation 

 in non-living systems but the term en- 

 zyme is reserved for the catalyzers found 

 in organisms. 



The importance of enzymes is very 

 great since most life processes are pro- 

 foundly influenced by them. In view of 

 this we may ask whether they constitute 

 a criterion of life. Cells may be killed 

 in a variety of ways which do not destroy 

 the enzymes and in that case the en- 

 zymes may be extracted from the dead 

 cell. In natural death the enzymes con- 

 tinue to work after death and the cell 

 undergoes a process of partial seK-diges- 

 tion known as autolysis. 



In some cases the action of enzymes 

 may be imitated by simple inorganic 

 substances, such as colloidal metals. 



The special function of oxidizing en- 

 zymes (and associated substances) is to 

 activate the inert oxygen of the air and 

 cause it to combine with various sub- 

 stances in the organism. Such enzymes 



