AVERY, MACLEOD, MCCARTY 



185 



Table III 



Differential Heat Inactivation of Enzymes in Dog and Rabbit Senim 

 Which Destroy the Transfortning Substance 



* Dilution of the digest mixture of serum and transforming substance. 



the transforming principle. The fact 

 that this difference in temperature of 

 inactivation is not merely a general 

 property of all enzymes in the sera is 

 evident from experiments on the heat 

 inactivation of tributyrin esterase in 

 the same samples of serum. In the latter 

 instance, the results are the reverse of 

 those observed with depolv-merase 

 since the esterase of rabbit serum is al- 

 most completely inactivated at 60°C. 

 while that in dog serum is only slightly 



affected by exposure to this tempera- 

 ture. 



Of a number of substances tested 

 for their capacity to inhibit the action 

 of the enzyme known to destroy the 

 transforming principle, only sodium 

 fluoride has been found to have a sig- 

 nificant inhibitory effect. Regardless 

 of whether this enzyme is derived 

 from pneumococcal cells, dog intesti- 

 nal mucosa, pancreatin, or normal sera 

 its activity is inhibited by fluoride. 



