ANTI-ENZYME IMMUNITY 277 



The bacterial factor merits a further study from another angle. It 

 is a protein and is destroyed by the proteolytic enzymes trypsin, pepsin 

 or papain. 



Rothbard and Todd (1948) reported that the streptococcal protein- 

 ase digests both the fibrinolytic factor ("Streptokinase") and M protein 

 antigen. The latter two components are not, therefore, usually found 

 in the same cultures with proteinase. Chloroform activated serum pro- 

 tease has been found to digest gelatin, casein, hemoglobin, fibrinogen 

 and fibrin, and shows, in some respects, similarity to trypsin. Does the 

 fibrinolytic serum protease digest the streptococcal factor immediately 

 following the completion of its activating role? Or does the streptococ- 

 cal factor combining with the inhibitor component of the inactive 

 serum protease complex remain inactive and insensitive to the pro- 

 teolytic action of the activated enzyme? These questions may merit 

 consideration for a satisfactory evaluation of the results of kinetic 

 studies in fibrinolytic and activation processes. 



On this basis, the activation of the inactive serum-protease by strepto- 

 coccal factor would be governed by a stoichiometrical relationship and 

 not by a catalytic activation. That is, the streptococcal factor would 

 stoichiometrically combine with the inhibitor substance, possibly a 

 lipid, and thereby set free the active proteinase. In other words, the 

 affinity of the inhibitor substance for the streptococcal factor would 

 be greater than its affinity for the serum protease: 



[Inhibitor-protease] -|-Streptococcal factor 



1 

 [Streptococcal f actor-Inhibitor] -)-protease 



The recent observations by Ratnoff (1948) would seem to be most 

 significant in this connection. Reinvestigating the problem of whether 

 or not the activation of serum by streptococcal factor is catalytic, he 

 arrives at the conclusion that his data indicate that "in the presence of 

 some substance altered by chloroform or heat, the activation of plasma 

 proteolytic enzyme by streptococcal factor behaved as if it involved a 

 stoichiometric reaction. Streptococcal factor seemed to react in molec- 

 ular proportions with a substance in plasma euglobulin which limited 

 the activation of plasma proteolytic enzyme." In disagreement with the 

 claim of Christensen, et ah, ascribing a catalytic role for streptococcal 

 factor, Ratnoff finds that the proteolytic activity evoked by this factor 



