ENZYME STUDIES OF LOWER FUNGI 41 



are not definitely associated with a particular substratum and 

 their identification is not so simple a matter. Most of these 

 molds readily adapt themselves to artificial cultivation, and for 

 that reason the study of their enzymotic activities is much facil- 

 itated. The power of adaptation to artificial surroundings is 

 so pronounced that a single definite crystalline substance may 

 be supplied as the sole source of carbon or nitrogen in the nutri- 

 tive medium, and the changes which it undergoes are therefore 

 comparatively easy # to follow. 



The pioneer work of Pasteur in the domain of biochemistry 

 led other investigators into the field and it was soon noted that 

 saprophytic molds had the power of utilizing a number of definite 

 chemical substances as sources of carbon and nitrogen. Since 

 molds cannot utilize solar energy as do the higher plants, their 

 metabolic activity is dependent upon exothermic chemical reac- 

 tions which they institute in the culture medium. These reac- 

 tions are, for the most part, of an oxidative nature. In the case of 

 the more complex substances as proteins and polysaccharides, 

 however, the substance must first be broken up into simpler com- 

 pounds, and oxidation is therefore preceded by hydrolysis. 



The formation of intermediary products by hydrolysis, whereby 

 the original molecule combines with water and then splits into 

 two simpler molecules at the point where the water enters, can 

 be studied in the laboratory by comparatively simple methods. 

 This type of reaction, corresponds exactly with the changes which 

 the three great classes of food materials, the proteins, fats and 

 carbohydrates, undergo in the alimentary tract of animals, pre- 

 liminary to absorption. As in the case of the higher animals, so 

 with these molds, the preparatory changes to which the complex 

 food material is subjected are brought about through the agency 

 of enzymes or digestive ferments. Since the activity of the 

 enzymes, under suitable conditions, survives the death of the 

 cell, the former can be made to manifest their activity in the 

 absence of life. This is where a series of most interesting results 

 has been obtained. The number and diversity of chemical sub- 

 stances which undergo hydrolysis when brought into contact with 

 aqueous extracts from the dead mold cells is indeed surprising. 



