Part 111 



Antibody as a Specific Enzyme 

 Inhibitor 



THE THEORY formulated in this treatise considers humoral immunity 

 as resulting from a biocatalytic process. This theory links the anti- 

 gens with enzymes. As discussed in Part I, the antigenicity of all the 

 simple and conjugated proteins is due to the catalytic activity of the pro- 

 tein molecule proper.* Similarly the catalytic activity of simple protein 

 enzymes such as pepsin, trypsin, urease, d-ribonuclease, etc., and that 

 of conjugated protein enzymes such as heme-, copper-, alloxazine-, 

 thiamine pyrophosphate- and pyridine-proteins is dependent on the 

 protein molecule proper. The prosthetic groups fer se (haptens of con- 

 jugated antigens, and coenzyme groups of conjugated protein enzymes) 

 are incapable of catalytic activity either as antigens or as enzymes. In 

 both instances the protein molecule, as part of the antigen or the 

 enzyme must therefore be looked upon as the basic biocatalytic unit. 

 Since 'practically all -proteins are antigenic the conclusion appears to he 

 inescapable that all proteins are endowed with catalytic activity of the 

 particular kind under discussion.^ 



There is no doubt that there will be arguments raised against the 

 inclusion of antigens among the enzymes. Such protests, however, must 



*By definition an antigen must exhibit two properties: (1) the power of stimulat- 

 ing the production of antibody in vivo; (2) the power of combining specifically with 

 this homologous antibody. Antigenicity has been ascribed to materials which give 

 in vitro precipitation of complement fixation (Wassermann "antigen") but do not 

 produce in vivo measurable antibodies. This loose usage of the term "antigen" may 

 cause some confusion. In this treatise the term "antigen" implies the original defini- 

 tion as given above. 



There may be non-protein substances which may prove to be truly antigenic, e.g. 

 acetylated polysaccharide. If this does occur it is difficult to know whether the anti- 

 genicity is due to this polysaccharide alone or due to the combination of this poly- 

 saccharide and an in vivo protein to form a complete antigen. 



tBergmann (1938) stated that "The essential substances transmitted from one 

 generation of cells to the next must be enzymes, and that they have to be enzymes 

 gifted with the capability of synthesizing individual proteins by predetermined 

 sequence of specificity reactions. . . . Therefore the proteinases owe their existence 



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