302 IMMUNO-CATALYSIS 



The substance in testicular extract, assumed to be the activator of 

 the clotting factor, is reported to be a protein, non-dialyzable, and, 

 possibly, antigenic. If we make an attempt to harmonize these proper- 

 ties of the activator substance and the clotting factor with the plasma 

 clotting reactions described above we may, perhaps, be permitted to 

 suggest the following interpretation as the probable course of the 

 reactions. 



The staphylococcal clotting factor may represent a complex consist- 

 ing of lipid-like substance and X-component. The X-component blocks 

 the activity of the lipid-like substance, keeping it in an inactive state. 

 The X-component manifests a greater affinity for a certain serum com- 

 ponent and testicular material (used as activators), forming a non- 

 dissociating or weakly dissociating complex. Under these conditions 

 the lipid-like component of the staphylococcal factor would be set free 

 to convert prothrombin to thrombin, the latter converts fibrinogen 

 to fibrin clot. These suggestions may perhaps be schematized in the 

 following manner: 



Clotting factor :^ Lipid-like active substance -\- X-component 



Serum 



or 

 testicular 



protein(?) 



Lipid-like active substance -|- serum or testicular protein-X complex 

 Prothrombin -|- staphylococcal lipid-like substance — > thrombin 

 Plasma fibrinogen -\- thrombin — > fibrin clot 



The degree of affinity of the X-component for the species serum or 

 testicular proteins would appear to determine the amount of uncom- 

 bined active component of the staphylococcal clotting factor at a given 

 temperature. The non-clotting behavior of guinea pig plasma at 37°C. 

 and its clotting at 20°C. for example, would point to a greater dissocia- 

 tion of X-plasma protein complex at 37°C. than at 20°C.:* 



37°C. 

 X-Protein complex t ^ Protein (of guinea pig or mouse plasma) -f- X 



20°C. 



the action of commercial enzyme preparation may involve the hydrolysis of a lipid- 

 like or polysaccharide-like substance, and not a protein. 



*In connection with the temperature effect on serological reactions the following 

 observations are of interest. Fihtti-Wurmser and Jacquot-Armand ( 1947a, 1947b) de- 



