260 IMMUNO-CATALYSIS 



antigens of streptococcal strains of Group A. It digests also fibrin, 

 casein, milk, gelatin and streptococcal fibrinolytic factor. The enzyme 

 is activated under the reducing conditions of active bacterial growth 

 and by cysteine, glutathione, thioglycollic acid, and potassium cyanide; 

 it is inactivated by iodoacetic acid. This enzyme was differentiated 

 from streptococcal hemolysin, hyaluronidase or fibrinolytic factor. 



Todd (1947) studied the serological specificity of the streptococcal 

 proteinase. He found that the antiproteinase activity of serum from 

 horses immunized with streptococcal proteinase was increased as much 

 as 200 times above the original level. The antiproteinase sera were in- 

 effective against other proteolytic enzymes. That the increased anti- 

 proteinase activity of the immunized animals was due to the presence 

 of a specific antibody was shown by a lack of a similar increase in anti- 

 proteinase activity in animals immunized with tetanus toxoid, diph- 

 theria toxoid and erythrogenic streptococcal toxin. The sera of animals 

 immunized with these toxoids contained respectively 10, 10, and 

 units of antiproteinase per ml., while a sample of serum from a normal 

 horse in the same stables contained 10 units of antiproteinase per ml. 

 A horse was immunized for 1 5 months with streptococcal erythrogenic 

 toxin. Both before and after immunization, the serum of this horse con- 

 tained no demonstrable antiproteinase. A sample of concentrated serum 

 from the pooled bleedings of horses immunized with erythrogenic toxin 

 contained 3,300 units of antibody to toxin and only 20 units of anti- 

 proteinase. These experiments show that antiproteinase activity does 

 not develop in the sera of horses immunized with antigens which do 

 not contain streptococcal proteinase. 



Antiproteinase is in the globulin fraction of both normal and im- 

 mune sera. Heat abolishes the normal trypsin inhibiting activity of 

 serum but was found to have no effect on the antiproteinase activity 

 of the serum. The trypsin inhibitor had no demonstrable neutralizing 

 activity for streptococcal proteinase. 



c. Differences of the Proteinases of CI. Sporogenes and CI. His- 

 tolyticum and the Specificity of the Anti-Proteinases. Blanc and 

 Pozerski (1920) studied the proteolytic enzymes of CI. sforogenes and 

 CI. histolyticum in comparison with pepsin, trypsin and papain. The 

 bacterial proteinases, unlike pepsin, were inactive at pH 5.5. They 

 hydrolyzed protein to the amino acid stage whereas pepsin stops at the 

 peptone stage of protein hydrolysis. The bacterial proteinases, like 



