ANTIBODY AS A SPECIFIC ENZYME INHIBITOR 173 



dent that guanine as the reaction product of hydrolysis is a strong 

 inhibitor of nucleosidase. While adenine exercises slight inhibitory 

 effect, its deamination product, hypoxanthine, exercises greater inhibi- 

 tion. In contrast, the deamination of guanine to xanthine deprives the 

 inhibitor of its effect on the enzyme. Five mg. of desoxyribose, one 

 of the reaction products of hydrolysis, exercised only 10 per cent 

 inhibition. Five mg. of each of the following substances: fructose, 

 glucose, uracilriboside, cytosinedesoxyriboside, yeast and muscle 

 adenylic acid, yeast and thymus nucleic acids, riboseguanilic acid 

 were entirely ineffective. 



13. Conclusion 



In the preceding pages numerous experimental facts have been dis- 

 cussed showing how in reaction systems catalyzed by enzymes, 

 substances are formed as final reaction products which specifically 

 combine with the enzymes and inhibit their activity. This specific 

 inhibition appears to compare with the inhibition of the biological 

 activity of antigenic substances by antibodies which as final reaction 

 products result from the catalytic action of antigens in vivo. 



It would have been more expedient perhaps if we could have 

 found examples from synthetic processes catalyzed by enzymes for a 

 direct comparison with the production of antibodies resulting from the 

 catalytic influence of antigens during the synthesis of globulins. 

 As our knowledge of the mechanism of complex synthetic enzyme 

 processes is very fragmentary, such a comparison was not possible. 

 However, since as both processes are catalyzed, and in each case the 

 final reaction products act as inhibitors on their respective enzyme 

 systems, we believe the comparison is well within the limits of sound 

 reasoning. 



Our view concerning the synthesis and production of antibody as 

 catalyzed by antigen differs from the theoretical basis of the experi- 

 ments carried out by Pauling and Campbell (1942). We believe that 

 antigen catalyzes and directs the synthesis of globulins from amino 

 acids or polypeptides (see pp. 120, 156) in a specific direction to yield 

 the homologous antibody globulin. Pauling and Campbell, on the 

 other hand, have experimented udth and advanced the idea that the 

 complete globulin molecules can be converted into antibody molecules. 



