ANTIGENS AS BIOCATALYSTS 47 



the protein do not initiate the formation of, but contribute to the 

 architectural pattern (specificity) of the antibodies. It is immaterial 

 whether a protein is used in its natural form or after having been 

 coupled with a chemical group non-existent in nature. The coupled 

 prosthetic groups which merely influence the specificity of antibodies 

 are comparable to the type or group specific carbohydrates of various 

 bacterial antigens. The prosthetic groups of artificial or natural con- 

 jugated antigens in many respects are similar to the conjugated en- 

 zyme proteins. In conjugated protein antigens the prosthetic groups 

 alone are non-antigenic; similarly the prosthetic groups of the con- 

 jugated protein enzymes are catalytically inactive by themselves. The 

 heme group in hemoglobin, catalase and peroxidase is comparatively 

 inactive without a combination with their specific native proteins. 

 Various co-enzymes must likewise be in conjugation with specific 

 proteins to manifest their activity. 



