514 



SELMAN A. WAKSMAN 



grown on Czapek's and Peptone-Czapek solution and the fil- 

 trates only used for experiment. 



The results brought out in the above experiment show a dis- 

 tinct difference between the activities of microbial and animal 

 proteolytic enzymes. In most instances the substratum neutral 

 to litmus contained a larger quantity of amino nitrogen; at 

 least the more alkaline reaction did not .prove more favorable 

 for the enzyme activities of microorganisms than the more acid 

 reaction. This would seem to point to several conclusions: 

 either the organisms produce a mixture of two enzymes which are 

 peptic and ereptic in nature, or, if the enzyme is of a tryptic 



TABLE 2 



Influence of sugar content of the medium upon the proteolytic activities of the exo- 

 and endoenzymes of A. niger. 



SUGAR CONTENT OP MEDIUM 



Control 







1 per cent 



3 per cent 



5 per cent 



20 per cent 



Trypsin: 200 mgm 



MILLIGRAMS OF NH2=N PER 100 CC. OP SOLUTION 



1 per cent peptone 



Exoenzyme 



21.32 

 45.24 

 46.40 

 47.60 

 38.86 

 44.24 

 46.68 



Endoenzyme 



20.30 

 41.84 



44.72 

 50.56 

 45.80 



52.78 



1 per cent casein 



E.xoenzyme 



7.28 

 45.00 

 54.56 

 43.44 

 25.38 

 38.28 

 56.56 



Endoenzyme 



6.20 

 39.44 

 54.00 

 54.56 

 55.06 

 56.32 



nature, it is much less sensitive to an acid reaction than animal 

 trypsins are. Finally, the enzymes produced by the micro- 

 organisms studied may be of a nature entirely different from that 

 of the animal proteolytic enzymes, and may be comparable to 

 those found by Vines (1900-1910) in plants; the range of their 

 optimum reaction is certainly greater than that of corresponding 

 animal enzymes. A. niger and A. fuscus, both closely related 

 species, produced, in the case of casein, less amino nitrogen 

 with the more acid reaction, and the same thing held true for the 

 enzymes of A. niger and Act. sp. 101 grown on the peptone- 

 containing medium. 



