ANTI-ENZYME IMMUNITY 225 



Twelve rabbits were immunized. All but one of the immunized 

 rabbits contained anti-invertase antibody in their sera. 



To determine the retardation of invertase action by immune serum 

 initial velocities were measured (the velocity of invertase during the 

 first 10 per cent of the hydrolysis of sucrose being constant as measured 

 experimentally). The region ranging from pH 3 to 6.9 was investigated 

 and the optimal retardation of hydrolysis of glucose in invertase- 

 immune serum systems was found to occur at pH 6.5 to 6.9. 



Normal serum did not affect the velocity of invertase hydrolysis of 

 sucrose. Retardation of the hydrolysis of sucrose by the invertase- 

 anti-invertase system was the same, whether it was measured im- 

 mediately after they were mixed or after incubating for 12 to 24 

 hours. When the initial velocity of hydrolysis was measured by allow- 

 ing the immune serum to act on the particular preparation of invertase 

 used for immunization the retardation was 36.4 per cent. The in- 

 hibitions by the other sera ranged from 16 to 36.4 per cent. 



The experiments on the specificity of anti-yeast invertase showed 

 that the immune sera against yeast invertase had no effect on honey 

 or taka invertase, even though yeast and taka invertases are fruc- 

 tosidases of the same type, which showed that the two proteins dif- 

 fered antigenically. 



In precipitation tests the enzyme reacted with immune sera in dilu- 

 tions up to 1:20,000 to 1:25,000. In hydrolysis experiments the en- 

 zyme-serum mixtures contained 0.5 ml. of serum, and 9.5 ml. of the 

 400-fold diluted enzyme used for immunization and tested for the 

 precipitin reaction. In these tests the solid content of the enzyme was 

 1 : 400,000, which is well outside the limits of the precipitin reaction. 

 Yet retardation took place in this dilution of enzyme antigen. 



4. Enzymatic Synthesis of Serologically and Physiologi- 

 cally Active Polysaccharides 



The presence of serologically reactive polysaccharides in microorgan- 

 isms is a well-known fact. Of the most widely studied bacterial polysac- 

 charides those of pneumococci have been the subject of considerable 

 interest (Heidelberger and Landsteiner, 1923; Avery and Goebel, 

 1933; Sevag, 1934; Goebel, 1936; Hotchkiss and Goebel, 1937; Goebel, 

 et at, 1939; Brown, 1939; Heidelberger, et al, 1942, 1946; Ivanovics, 



