328 IMMUNO-CATALYSIS 



hemolysis takes place. The hemolysis of a single red cell, it was thus 

 presumed, is an "all-or-none" process. 



One hemolytic unit of streptolysin O was found to contain 5X10~^ 

 mg. of nitrogen, which compared satisfactorily with the activity of 

 pneumococcal hemolysin containing 2.4XlO~^ mg. N per 1 H.U. 

 Our calculation showed that 9.08X10^ molecules of pneumococcal 

 hemolysin were needed to hemolyze one red blood cell. Assuming that 

 the molecular weights of streptolysin and pneumolysin are comparable 

 the same number of molecules of the hemolysins should produce an 

 equal hemolytic effect. On a weight-to-weight basis the activity of 

 streptolysin will thus show a ratio of about 1 : 53,280 (see page 323). 



Herbert and Todd stated that 0.02 M iodoacetic acid had no effect 

 on streptolysin O when kept with it for 20 minutes at room tempera- 

 ture, and only a slight effect (22 per cent inhibition) at 38° C. With 

 0.02 M iodoacetamide, which is considered to react with protein -SH 

 groups more readily than iodoacetic acid, only partial inhibition (66 

 per cent) resulted. These results only partially agree with those of 

 Smythe and Harris (1940). 



b. Probable Enzymic Nature of Bacterial Hemolysins. The reac- 

 tivation of inactive hemolysin by hydrosulfite, cysteine or a number of 

 reducing agents makes it resemble a number of enzymes which are 

 similarly affected by oxidation and reduction. These enzymes, urease, 

 arginase, papain, cathepsin, succinic dehydrogenase, triosephosphate 

 dehydrogenases are strongly inhibited by low concentrations of iodo- 

 acetic acid. Maschmann (1937) also found that the clupeinase ac- 

 tivity of a toxin preparation of CI. welchii was activated by cysteine, 

 and while the proteolytic filtrates of vihrion se^tique and B. hotulinus, 

 types A and B, had no action on clupein, in the presence of cysteine 

 they were rendered strongly proteolytic. The findings of Maschmann 

 on these enzymes are, therefore, in agreement with the findings on 

 the properties of hemolysins originating from bacterial filtrates. 



Inactivated streptolysin O is not adsorbed by red cells, while the 

 active form is, and it is suggestive that the -SH groups are necessary 

 to attach the hemolysin to the red cell. This, however, cannot be too 

 strongly supported in view of the fact that potassium cyanide, the 

 activator of many of the above enzymes, fails to activate streptolysin 

 O appreciably. Furthermore, streptolysin unlike these enzymes is re- 

 sistant to the action of iodoacetic acid. 



