PROTEOLYTIC ENZYMES OF SOIL FUNGI 



523 



enzymes of the microorganisms used can decompose peptone and 

 casein, but this does not tell us with what group of enzymes 

 these should be classified, whether with the trypsins or with the 

 erepsins, both of which, when obtained from animals, split pep- 

 tone and casein. But these are active only in alkaline solutions, 

 while the enzymes of the microorganisms studied act best in 

 neutral and even slightly acid media. This would seem to indi- 

 cate that the latter do not belong to the same class of enzymes 

 as those obtained from animal tissues. Went (1901), Butke- 

 witch (1903), Saito (1903), and Franceschelh (1915) claimed 

 that we are dealing with trypsins. The work of Dox (1910) 



TABLE 8 



Influence of temperature of incubation upon the activities of the proteolytic enzymes 



of A. niger 



Reed and Stahl (1911), Berman and Rettger (1916) and others 

 would lead us to think that we are dealing here with erepsins, 

 which may be very close to animal erepsin. The work of Vines 

 (1900-1910) on the enzymes of plants and those of Aspergillus 

 oryzae and the studies of Hagem (1910) tend to prove that we 

 have here a mixture of peptases and ereptases more closely allied 

 to the corresponding plant enzymes than to the animal enzjones. 

 The fact that certain investigators have obtained the liquefac- 

 tion of gelatin, which resulted in the production of peptone, by 

 the enzyme of A. niger leads us to think that this organism pro- 

 duces enzymes which, besides being of an ereptic nature, are also 

 tryptic or peptic in nature. The work of Malfitano (1900) and 



