ANTIBODY AS A SPECIFIC ENZYME INHIBITOR 159 



reaction products are formed in due course. By virtue of the structural 

 similarity to the substrates from which they are formed, these products 

 exercise specific affinity for the enzymes in accordance with the mass 

 action law, in the same manner as antigens combine with antibodies. 

 The degree of inhibition is dependent on the degree of affinity for the 

 enzyme and the amount of the inhibitor produced. The consequences 

 of the reaction of the enzyme molecule with its reaction product as 

 inhibitor, is comparable in every respect with the reaction of antigen 

 with the antibody which has resulted from the action of antigen 

 in vivo. The inhibitor produced by one enzyme will not inhibit another 

 enzyme. It is therefore highly specific in the same way that an antibody 

 will not combine with a heterologous antigen. 



5. Zinsser's View on the Formation and the Role of 

 Antitoxins 



Northrop (1922) in his studies on the kinetics of the action of 

 pepsin and trypsin on protein observed certain divergences which he 

 explained by the production of hydrolytic products acting as inhibitors. 

 These inhibitory products combining with the enzyme maintained an 

 equilibrium which obeyed the ordinary mass action law. The diges- 

 tion of protein by pepsin, combined with such substances as peptone 

 (the word "peptone" used broadly as signifying substances in solution 

 with which the pepsin combines without hydrolyzing them), was not 

 proportional to the total concentration of the pepsin. He therefore, 

 believed that as the pepsin digested the protein, peptone-like substances 

 are formed with which pepsin combined and with which it then 

 maintained an equilibrium following the mass action law. In adding 

 increasing amounts of peptone to pepsin solution, as a result of this 

 manner of combination, the first amounts added inactivated more 

 pepsin than the latter additions, which Northrop pointed out is in very 

 striking analogy to the manner in which antitoxin and toxin react. 



In the case of trypsin as it acted on the undigested protein solution 

 trypsin inhibiting substances were also formed. The activity curve 

 showed that, at first, there was a very rapid drop of activity which 

 gradually became slower. 



Hans Zinsser (1923) in his discussion of toxin and antitoxin stated 

 that a good deal of light may be hoped for in regard to the nature of 



