ANTIBODY AS A SPECIFIC ENZYME INHIBITOR 147 



by Sumner and his associates to affect urease in a manner comparable 

 in every respect to those exercised by antitoxins on toxins of various 

 origin. 



1. Serological Specificity of Stereoisomeric Conjugated- 

 Protein Antigens 



Since the statement made by Ehrlich that the specificity of toxin- 

 antitoxin reactions is analogous to the specificity of fermentation re- 

 actions there has not been any systematic study to define clearly what 

 this analogy consists of. During the last two decades the investigations 

 with artificial conjugated antigens have yielded valuable data which 

 have defined satisfactorily the role of determinant (prosthetic) groups 

 on the specificity of the reactions with these antigens. Pioneering work 

 in this field has been carried out by Landsteiner and his associates, 

 and Avery, Goebel, and associates. Landsteiner (1936) formulated 

 his findings as follows: There are striking differences among aro- 

 matic compounds, isomeric with respect to the position of substitu- 

 ents in the benzene ring, and the gradation in their cross reactions is 

 to be taken as a definite indication that spatial structure, as well as 

 chemical constitution in the ordinary sense of the word, plays an im- 

 portant role in serum reactions, "as had been shown for enzymatic 

 processes by E. Fischer, and frequently confirmed. Hypothetically, 

 Fischer's conception had been applied by Ehrlich to the investigation of 

 serum reactions." 



On immunizing animals with azo-proteins of d- and l-phenyl-(para- 

 aminobenzoylamino)-acetic acids: 



H H 



~\ I I 



Protein— N = N—< >— C— N— C 



O COOH 



d-isomer 



H COOH 



Protein— N = N—< ^C— N— C 



O H 



1-isomer 



