MECHANISM OF ANTIBODY FORMATION 117 



all antigens fulfill the requirements of the criteria of ideal catalysis, 

 they must, therefore, be considered as catalysts. Since all proteins 

 are antigenic, they exhibit, therefore, biocatalytic activities. In Nor- 

 throp's postulates, our concept of antigens acting as catalysts has under- 

 gone a variation by which antigens have been considered as acting as 

 coenzymes. This variation contains certain concepts of the mechanism 

 of antibody formation fundamentally different from ours. His antigenic 

 coenzyme is supposed to be capable of initiating autocatalytic con- 

 version of normal to antibody globulin. In contrast, our concept deals 

 with a mechanism of the development of the specificity of antibody 

 globulin structure preceding the completion of the synthesis of a 

 normal globulin molecule, under the directive influence of the active 

 units of the antigenic molecule. In other words, the sfecifLcity of an 

 antibody molecule is the consequence of specific cellular synthethic 

 fwcesses catalytically inodified hy an antigen to conform with the 

 configuration of certain active groups of the antigenic molecule. 



The use of the term coenzyme to account for the postulated role 

 of antigen in connection with the formation of specific antibodies intro- 

 duces confusion. A comparison, therefore, of the role of coenzymes 

 in respiratory processes, and the role of antigens in the formation of 

 antibodies seems to be required. Haptens, which constitute the 

 prosthetic groups of conjugated antigens, are incapable of inciting the 

 formation of specific antibodies without combination with a protein. 

 This would indicate that the catalytic role of an antigen resides in 

 the protein molecule and that only in this combination can a hapten 

 exercise its determinant function. The coenzyme groups of the 

 respiratory enzymes are likewise inactive when not in combination 

 with specific proteins. The same coenzyme group seems to function 

 exclusively with certain specific proteins, and not with all proteins, 

 yielding a group of related enzymes, for example, flavoproteins, each 

 characterized by distinctive specificity of action. This specificity resides 

 in the protein molecule and not in the coenzyme group. On the other 

 hand, in immune reactions if the conditions permit, the same hapten 

 can be combined with any antigenic protein to demonstrate its 

 determinant characters. In this respect, a hapten is not selective. In 

 these combinations, both the protein and the hapten produce anti- 

 bodies, respectively specific. 



In conjugated enzymes, neither the specific protein nor the coenzyme 



