EXPERIMENTS WITH BACTERIAL ENZYMES 135 



In respect to passage through the Berkefeld bougie, therefore, the 

 bacterial gelatinases agree with ptyalin and taka-diastase rather than 

 with rennet (cf. Levy, op. cit.). 



CONDITIONS OF ENZYME ACTIVITY. 



Reaction It is well known that the acid or alkaline reaction of 

 the medium in which an enzyme is present often exercises great 

 influence upon the activity of the enzyme. As regards the parti- 

 cular enzyme under consideration, it seems to have been generally 

 assumed that the gelatin-liquefying enzymes produced by bacteria 

 were most potent in an alkaline medium. Thus Abbott and Gilder- 

 sleeve 1 state: 



As is the case for the majority of proteolytic enzymes, be thfeir origin wha 

 it may, we find our filtrates to be uniformly more active when they are of alkaline 

 than of neutral or acid reaction. When acidified they are as a rule inactive. In a 

 simlar manner their production by the growing organism is always more marked in 

 alkaline than in either neutral or acid media, even though the latter is not sufficient 

 to depress growth to any marked extent. 



Further details are not given in their paper. 



The statement that gelatinase production is more marked in alka- 

 line than in neutral or acid media, evidently needs some qualification 

 in view of the facts set forth in another part of this paper (p. 130). 

 It by no means follows that the initial reaction of the culture medium 

 represents the conditions under which the enzyme is produced. A 

 gelatin culture and a broth culture of a liquefying species diverge in 

 respect to reaction from the moment growth begins to take place, the 

 gelatin culture invariably becoming more acid. 



The fact that gelatin liquefied by enzyme action has a strongly acid 

 reaction seems to have been generally overlooked by bacteriologists.* 

 The products of gelatin digestion comprise glycocoll, aspartic acid, 

 and glutaminic acids, and other acid substances. When, therefore, 

 any one of the bacterial gelatinases, or, for that matter, Griibler's 

 pancreatin, is added to gelatin, the substances produced by the enzyme 

 action impart a strongly acid reaction to the liquefied mass. In most 

 liquefied gelatin cultures of bacteria the reaction ranges as high as 

 2 . o per cent to 3 . o per cent acid to phenolphthalein, and in some cases 

 it is over 4.0 per cent. By the very conditions of its action, then, a 



*Loc. cit. t p. 47. 

 * I have discussed this elsewhere, Science, February 9, 1906, p. 220. 



