ACTION OF THE ENZYMES. 155 



dried. The resulting white powder keeps for a long time, 

 and when dissolved in water shows great diastatic ac- 

 tivity. 1 



The inversion of cane-sugar as catalyzed by sucrase is 

 markedly influenced by time, concentration of the ferment, 

 temperature, and other external conditions. In infinite time 

 a small amount of the ferment brings about as much change 

 as a larger amount. If the products of the reaction (dextrose 

 and laevulose) are not removed, the reaction is incomplete, 

 and when the catalysis has come to a standstill all three sub- 

 stances are present in the reaction mixture. It is ordinarily 

 said that the products of the reaction interfere with the action 

 of the enzyme a fact which we have learned before in the 

 consideration of most of the other ferments. The catalysis 

 of the cane-sugar under the influence of sucrase, and the 

 catalysis of the same substance under the influence of acids 

 which bring about the same chemical change in the sucrose 

 differ in this regard, for no limit is reached when acids are 

 employed, the inversion being in this case complete. 



Only when the concentration of the ferment is high, the 

 temperature low, and the experiment continued for but a 

 short time does an almost constant relation exist between 

 the concentration of the ferment and the amount of invert- 

 sugar formed. This explains, for example, the results of 

 O'SuLLiVANandToMPSON, who believed that the catalysis of 

 cane-sugar under the influence of sucrase was governed by 

 the same laws as the catalysis under the influence of acids. 

 In every experiment which is continued a sufficient length 

 of time, the amount of invert-sugar formed in the unit of 

 time from the sucrose in the presence of sucrase gradually 

 diminishes. The point at which the reaction comes to a 

 standstill varies with external conditions of temperature, 

 concentration of the reaction mixture, etc. But only when 



1 See EFFRONT: Die Diastasen. Translated into German by BUCH- 

 ELER, Leipzig, 1900, 1, p. 59. 



