ANTIGENS AS BIOCATALYSTS 25 



meric forms, or two or more isomeric forms at a state of equilibrium 

 contain the catalyst as part of the molecule. 



Let us turn now to the production of antibody in the light of what we 

 know about chemical changes. As discussed in the preceding pages, 

 if the production of a new substance is brought about by the union 

 of two reacting substances, then the reaction product or products 

 should contain parts of the reactants according to stoichiometrical 

 relationship. If on the other hand, such a reaction is accelerated by 

 the presence of a substance which does not enter into the union irre- 

 versibly with the reaction products, the role of this substance is one of 

 catalytic acceleration. 



The absence of the catalyst or its parts in the final products of a 

 catalytically accelerated reaction is one of the fundamental criteria 

 of catalysis. If it can be demonstrated that the antibody formed in 

 response to an antigenic substance does not contain the antigen 

 molecule or its parts, the formation of the antibody can be assumed to 

 have taken place by the antigen acting as catalyst. If, on the other 

 hand, a chemical union has taken place between the antigen and the 

 tissue substances forming the antibody complex, then this complex 

 must be produced in accordance with stoichiometrical principles. The 

 answer to this question must come from analytical and quantitative 

 studies. 



3. Characteristics Which Are Common to Inorganic 

 Catalysts, Enzymes and Antigens 



Before we present the facts concerning the quantitative relationship 

 between antigen and antibody produced, let us discuss what a catalyst 

 is. For later discussions it is also necessary at this point to specify the 

 difference that exists between an inorganic catalyst on the one hand, 

 and the enzymes or biocatalysts on the other. The inorganic catalysts, 

 no doubt, exist in nature and are produced under natural conditions. 

 However, modern chemistry has produced quite a large number of 

 inorganic catalysts in the laboratory as the need may have demanded, 

 or they are accidentally discovered. These are, therefore, artificial 

 catalysts. All the enzymes or the biocatalysts without exception, on the 

 contrary, are produced by living systems. An enzyme is a complex 

 organic substance produced by a living cell and utilized by the cell 



