224 



VEGETABLE ENZYMES. XVIII 



The mean results of three such series, corrected for blanks, each at 

 pH 4, 6, and 8, are given in Table III. 



TABLE III. 



Actions of Potato Juice in Presence and Absence of Sucrose. 



The results in the last two columns show the presence of a sucrose- 

 hydrolyzing enzyme much more active in the slightly acid (pH 4) 

 solution when acting upon potato juice plus sucrose. 



The presence of a maltase in potato juice was tested for in a similar 

 way by using 1 per cent maltose solutions in place of 1 per cent 

 sucrose solutions. The results are given in Table IV. 



TABLE rv. 



Actions of Potato Juice in Presence and Absence of Maltose. 



No maltase is present in the juice as prepared as far as can be told 

 from these results. The one small positive action obtained on the 

 juice appears to be within the limits of experimental error. The 

 added maltose acts in fact to retard the actions, especially markedly 

 in connection with the action on the added starch. Because of the 

 complexity of the reactions involved in the hydrolysis of starch, this 

 does not appear to be a mass action effect of the products of the 

 reaction retarding further action, but can better be referred to an 

 action between maltose and the amylase, possibly a chemical combi- 



