246 B. CINADER AND J. H. PEARCE [13 



in soluble antigen-antibody complex but to a decrease in the enzyme activity 

 of the precipitates of antigen and antibody. 



So far little is known from direct experiments about the specificity of 

 antibodies to native proteins. Experiments by Landsteiner and van der 

 Scheer (1934) and of Landsteiner (1945) with peptide azo proteins have 

 indicated that the specificity of the antibody may correspond to at least 

 5 amino acids, but this is a minimum estimate in a system which may not 

 represent an adequate model for a native protein. The work of Porter pre- 

 sented in this symposium (p. 290) and observations recently published by 

 Lapresle (1955) thus constitute a valuable advance of this problem. 



The studies of Moore and of his colleagues are rapidly unravelling the 

 detailed structure of ribonuclease, thus presenting us with known polypep- 

 tides which might be used to inhibit the reaction between ribonuclease and 

 its antibody. The enzyme nature of ribonuclease would permit studies in 

 which antibody action could not only be inhibited in terms of precipitation 

 between enzyme and antibody, but also in terms of the effect of antibody 

 on enzyme action. 



Thus the collaboration of enzyme-chemist and immuno-chemist may not 

 only advance our knowledge of antibody specificity but may even result in 

 some information on the nature of the catalytic site of enzymes. 



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