44 IMMUNO-CATALYSIS 



decomposition, tautomerism and mutarotation. A catalyst does not 

 change stoichiometrical relationships of reactions, does not enter into 

 any irreversible stable union either with the reactants or with the 

 reaction products; its function is therefore one of repetition and con- 

 tinuity. For this reason it can transform a disproportionately large 

 amount of substrates into reaction products. Numerous examples have 

 been cited to emphasize this property of inorganic and organic catalysts 

 (enzymes). Antigens likewise have been shown to produce dispropor- 

 tionally large amounts of antibodies. Catalysts and enzymes in no case 

 have been shown to be part of the reaction products; similarly, highly 

 sensitive qualitative and quantitative analytical tests have not been 

 able to demonstrate the presence of antigens or their parts ("marked" 

 antigens) in the antibody molecules. It thus appears that antigens do 

 not function as reactants in the stoichiometrical sense in the formation 

 or synthesis of antibody molecules. The experimental data which have 

 been presented would therefore seem to show that the role of antigens 

 in stimulating the formation of specific antibodies is one of catalysis, 

 which fact brings the antigens within the class of biocatalysts. 



If antigens are believed to exercise a catalytic role in the production 

 of antibodies, enzymes likewise have been shown to demonstrate the 

 property of stimulating the production of specific antibodies. This 

 property of enzyme proteins has been a subject of controversy for many 

 years, although recently it has been accepted as an established fact. 

 Thus antigens and enzymes possess two properties in common- 

 catalytic activity and antibody production. These two properties are 

 interwoven in the production of antibodies. 



4. Do Catalysts (Antigens) Make a New Reaction Possible? 



The two properties of antigens and catalysts discussed above meet 

 two of the basic criteria of the concept of catalysis. These properties 

 are: (a) infinitesimal amounts of inorganic catalysts, enzymes and 

 antigens catalyze the interaction of disproportionately large amount of 

 reactants, and (b) neither antigens nor enzymes (and inorganic 

 catalysts) form a part of the reaction products. There is also another 

 criterion of the concept of catalysis which must be satisfied by enzymes 

 and catalysts as well as antigens. A catalyst can only accelerate (not 

 cause) a thermodynamically possible reaction. In other words, a catalyst 



