ANTI-ENZYME IMMUNITY 301 



potential enzyme. The assumption, therefore, that the activator sub- 

 stance converts the clotting factor to a thrombin-like substance, or 

 that the clotting factor is a precursor of thrombin-like substance is 

 negated by the above mentioned properties of the clotting factor, for 

 thrombin-hke substance must necessarily be of protein nature and 

 relatively heat-labile. The clotting factor has not been shown to exhibit 

 any of these properties. 



The thermostability of the clotting factor appears to compare with 

 the heat stability of thromboplastins. Confirming the findings of 

 previous investigators, Smith and Hale (1944) reported that staphy- 

 lococcal culture filtrates possessing strong clotting activity retained con- 

 siderable activity after heating for thirty minutes at 100°C. but with 

 a steady progressive loss of activity with time. Heating at 80°C. causes 

 some loss, complete inactivation is rapid at 120°C. No mention was 

 made of the use of an experimental precaution to exclude air-oxygen 

 during heating as a possible cause of oxidative inactivation of lipid-like 

 substances. 



Quick (1942) reported that thromboplastin when exposed to air 

 gradually turns brown and simultaneously with this a loss of activity 

 occurs. Exclusion of air protects it indefinitely, presumably by prevent- 

 ing oxidation. Quick determined the effect of heating on the thrombo- 

 plastic activity of rabbit brain and lung extracts. Heated at 54°C. for 

 15 minutes the clotting times for brain and lung extracts were, re- 

 spectively, 8 and 7.5 seconds; at 75°C., 25 and 12 seconds. Heated for 

 10 minutes at 100°C., they were, respectively, 37 and 15 seconds, and 

 heated for 60 minutes at 100°C. they were, respectively, 50 and 20 

 seconds. These results suggest a comparability between thromboplastin 

 and the clotting factor with respect to thermostability. A final under- 

 standing of the significance of this relationship requires critical analysis 

 of the chemical nature of the clotting factor.* 



* Walker, et al. (1947) reported that "coagulase" contains peptide linkages hydrolyz- 

 able by proteolytic enzyme preparations. However, in view of the fact that "coagulase" 

 resisted the action of 120° C. temperature for 20 minutes in the autoclave they raised 

 some doubt about its enzyme nature. They used 20 mg. of commercial trypsin (Pfan- 

 stiehl) and U.S. P. pepsin (Merck) to digest five ml. of the culture supernatant as 

 source of "coagulase." Both the U.S. Dispensary (1943) and U.S.?. (1947) state 

 that commercial proteolytic enzyme (pancreatin) is a substance containing enzymes, 

 principally amylase, trypsin, and lipase (steapsin). Since they used 20 ma. of com- 

 mercial enzyme all of these enzymes can be assumed to be present. In view of the 

 result of our analysis of the available data, indicating that "coagulase" may be a lipid 

 type of compound, and in view of the uncertainty of the antigenicity of "coagulase," 



