Studies in the Mechanism of Enzyme Action. 5 



optimum temperature of +47° is seen to obtain, and that no matter what 

 the enzyme concentration. 



Figs. 2 and 3, in the constancy of the optimum temperatures which they 



! J 1 ' ■■■ M.: .^ 1 „ 



TO 20 30 40 5C 60 

 TEMPERATURE *■ 



Fig. 3. — Subtrate concentration M/20. Enzyme concentrations 2 x 10~^ to 20 x 10~^ grm. 

 per cm.'' Eeaction of medium — natural reaction. 



respectively record, are very striking and indicate clearly the rdle of the 

 chemical reaction, or H"*" concentration, of the medium in fixing the optimum 

 temperature of the ferment. 



Actual measurements were made of tlie H"*" concentration, by Sorensen's 

 calorimetric method,* for the different enzyme dilutions employed in the two 

 foregoing series of experiments. For the natural reaction series (fig. 3), the 

 H"*" concentrations of the different dilutions were found to be all identical, 

 while the same was found to be true of the acid series (fig. 2), the two 

 distinctive values of Ph thus obtained being respectively as indicated in 

 fig. 1. 



The variation, then, of tlie optimum temperature of an enzyme with the 

 chemical reaction, or H"^ concentration, of the medium, previously established 



* ' C. R. Lab. de Carlsberg,' vol. 8, p. 148 (1909). 



