Lewis Knudson igi 



Why the increase in concentration of tannic acid should increase 

 the amount of tannase is difficult to explain. The amount re- 

 moved by the organism from the solution is undeterminable with 

 the present method of analysis. 



Is the stimulation produced within the cell, or is it caused by 

 contact of the tannic acid with the plasma membrane? , Tannic 

 acid precipitates albuminous substances, and it might be possible 

 that it reacts in this manner with the plasma membrane and this 

 precipitation might be the stimulus for the production of the enzy- 

 me. This explanation would not, however, include the stimulation 

 to production of the tannase by gallic acid. 



A suggestive explanation for the increase of the tannase with 

 increased concentration of the tannic acid is afforded by the work 

 of Katz.''^ In his experiments Katz found that diastase could be 

 precipitated by tannic acid and rendered inactive, though when 

 freed from the tannic acid by washing wiijh alcohol it becomes 

 active. Bearing in mind this precipitation by tannic acid and 

 working on the hypothesis that if the diastase formed and secreted 

 into the culture solution were removed from solution more diastase 

 would be formed, he added tannic acid to the culture solution, 

 assuming that in this way there should be an increase in the quan- 

 tity of the diastase formed. In his experiment Katz actually 

 found that the total quantity of enzyme formed (that secreted 

 into the nutrient solution and that present in the fungus) was 

 greater in the culture which contained 0.5 per cent tannic acid 

 than in the control, the ratio of the diastatic activity being 143 to 

 100. The results seem to confirm his hypothesis, but there are a 

 number of factors which suggest another explanation of the results 

 obtained. In some previous experiments^' of the writer it is 

 noted that in the presence of 10 per cent sugar the tannic acid was 

 fermented, and in table I, here reported, it is clear that even in 

 the presence of only 0.1 per cent tannic acid the enzyme tannase is 

 formed and in all probability secreted. The tannic acid of the 

 culture solution would, therefore, be fermented and rendered inac- 

 tive as regards its capacity to precipitate the diastase liberated, 

 and this condition doubtless occurred in the experiment of Katz. 



22 J. Katz: Die regulatorische Bildung von Diastase durch Pilze, Jahrb. 

 f. mss. Bot, xxxi, pp. 599-618, 1898. 

 2' Loc. cit. 



THE JOUBNAL OF BIOLOGICAL CHEMISTRY, VOL. XIV, NO. 3. 



