PROTEOLYTIC ENZYMES OF SOIL FUNGI 515 



When the activities of the enzymes are compared with regard 

 to the age of the culture, we find that the five-day-old cultures 

 gave, on the average, a higher amino nitrogen production from 

 both peptone and casein, and with both reactions. This is not 

 fully in accord with the idea of Dox (1910) that in the older 

 cultures the enzymes are excreted into the substratum, and the 

 liquid therefore becomes richer in enzymes. It is likely however 

 that the weakness of the enzymes in the older cultures may be 

 due to an accumulation of acids or other waste products in the 

 media, which might influence injuriously the activities of the 

 enzymes. 



That the enzymes produced by the organisms studied are not 

 merely pepsins can be seen by glancing at table 3. The peptone 

 was split just as well as the casein, giving amino-acids and other 

 simple amino-nitrogen-containing compounds, the identity of 

 which has not been established with certainty. 



The culture mediiun, on which the organisms were grown, 

 seems to have a decided influence upon the amount of enzymes 

 present in the medium. The peptone-containing medium gave 

 in all instances a much stronger proteolytic action than the 

 peptone-free medium; but even on the peptone-free media pro- 

 teolytic enzymes were also produced. This points to the fact 

 that the variation in enzyme production by microorganisms on 

 different media is not of a qualitative but of a quantitative 

 character, as has already been demonstrated by other investi- 

 gators. 



Small quantities of ammonia amounting to a few milligrams 

 of nitrogen per 50 cc. of solution were found in the substrata in- 

 oculated with the enzymes; this is probably due to the action 

 of the desamidasing enzymes, as was shown by Shibata (1902), 

 Pringsheim (1908), and Dox (1910). 



It was thought advisable to repeat the study of the influence 

 of reaction upon the enzyme activities of microorganisms. One 

 per cent peptone solutions were made up neutral to phenol- 

 phthalein, and divided into three portions; one portion was left 

 at that reaction and is termed "alkaline;" to a second portion 

 3 cc. of O.In HCl were added for each gram of casein or peptone, 



THE JOURNAL OF BACTBKIOLOGr, VOL. Ill, NO. 6 



