192 IMMUNO-CATALYSIS 



sion (containing Type II cells) was treated with Type II antiserum 

 agglutination took place. 



Conclusion 



In the preceding pages certain controversial aspects of the question 

 of the existence of anti-enzymes were analyzed. The points considered 

 no doubt apply primarily to impure enzyme preparations. In the light 

 of the above cited facts showing the absence of non-specific adsorption 

 of proteins on antigen-antibody precipitates,* the objections in this 

 regard appear to have been merely of a speculative nature. Further- 

 more, in studies in which crystalline or highly purified enzymes have 

 been used these objections are stripped of their power and are only 

 of historical interest. 



3. Effect of pH of Optimal Enzyme Activity on the 

 Nature and Extent of the Antigen-Antibody or Enzyme- 

 Anti-Enzyme Combinations 



Each enzyme exercises its greatest activity at a narrow range of pH. 

 Pepsin, for example, is most active at pH 2 to 3. In contrast trypsin 

 and papain function best at neutrality. ^-Amylase is most active at pH 

 5.2; /?-fructosidase (invertase), pH 4.5; a-glucosidase, pH 7.5 to 6.5; 

 in contrast, i8-glucosidase functions best at pH 3 to 6. The pH of the 

 optimal activity of bacterial enzymes varies. The cytochrome-cyto- 

 chrome oxidase systems function at neutrality; on the other hand, 

 carboxylases are most active at or around pH 6. In the study of the 

 nature of the combination between any one particular enzyme and 

 its homologous antibody it might appear necessary to work in a region 

 of acidity where the enzyme is most active. However, the pH of optimal 

 enzyme activity might not be the favorable one for complete enzyme- 

 antienzyme combination. It is necessary that the test be carried out at 

 a pH favorable for immune reactions. As a direct result of the 

 chosen pH the activity of the enzyme might be less than the optimum. 

 This, however, is unavoidable if we are interested in demonstrating 

 the inhibition of the activity of an enzyme by its homologous antibody. 



*This statement does not apply to the combination between the antigen-antibody 

 complex and the proteins comprised in complement. In complement fixation the com- 

 plement combines non-specifically with various antigen-antibody complexes. 



