ENZYMES AND THEIR ACTION 7 



substance termed enterokinase 1 (see page 196). These are examples of 

 many well-known activation processes going on continually within the 

 animal organism. The agency which is instrumental in activating a 

 zymogen is generally termed a zymo-exciter or a kinase. In the cases 

 cited hydrochloric acid would be termed a zymo-exciter and entero- 

 kinase would be termed a kinase. 



After filtering yeast juice, prepared by the Buchner process (see page 

 2), through a Martin gelatin filter, Harden and Young showed that 

 the colloids left behind and the nitrate were both inactive fermenta- 

 tively. Upon treating the colloid material (enzyme) with some of the 

 filtrate, however, the mixture was shown to be able to bring about pro- 

 nounced fermentation. It is believed that a co-enzyme present in the 

 filtrate was the efficient agent in the transformation of the inactive 

 enzyme. It is necessary to make frequent renewals of the co-enzyme 

 in order to maintain continuous fermentation. It was further shown 

 that this co-enzyme, in addition to being diffusible, was not destroyed 

 by boiling and that it disappeared from yeast juice when this latter 

 was fermented or allowed to undergo autolysis. The exact nature of 

 this co-enzyme of zymase is unknown. The co-enzyme action, in this 

 case, is probably dependent upon the presence of two individual 

 agencies, one of which is phosphates. 



It has been shown by Loevenhart that the property of acting as a 

 pancreatic lipase co-enzyme is vested in bile salts, and Magnus has 

 further shown that the synthetic salts are as efficient in this regard as 

 the natural ones. A few other instances of co-enzyme demonstrations 

 have been reported. 



Electrolytes are very important factors in facilitating or inhibiting 

 enzyme action. 2 For example, the Cl ion in proper amount facilitates 

 the action of amylases. 3 In fact the presence of the Cl or Br ion is 

 apparently absolutely essential to the activity of pancreatic amylase, 

 inasmuch as dialysis renders this enzyme inactive, the activity return- 

 ing on the addition of sodium chloride. 4 The acidity or hydrogen ion 

 concentration of the solution also exerts much influence on the activity 

 of enzymes. It has been demonstrated in the case of certain enzymes, 

 at least, that the continuous vibration or shaking of their solutions tends 

 to produce a destruction of the enzyme. Ultraviolet light also has a 

 destructive action on enzymes. 



The so-called " specificity" of enzyme action is an interesting and 

 important fact. That enzymes are very specific as to the character of 



1 According to Delezenne, trypsinogen may be rapidly activated by soluble calcium salts. 



2 For literature, see Kendall and Sherman: Jour. Am. Chem. Soc., 32, 1087, 1910. 



3 Wohlgemuth: B iochemische Zeitschrift, 9, 10, 1908. 

 4 Bierry: Ibid., 40, 357, 1912. 



