Concentration upon the Optimum Temperature of a Fer ment. 413 



practically all temperatures, although varying in amount from temperature 

 to temperature, subject to the influence — to be explained presently — of the 

 hydrogen ion concentration of the medium. 



As to the influence, if any, of the H + concentration of the medium on the 

 optimum temperature of the enzyme, fig. 2 clearly shows that for each H + 

 concentration there exists a perfectly definite optimum temperature; also, 

 the optimum temperature is seen to fall progressively as the H + concentra- 

 tion is increased beyond the optimum reaction of fig. 1. In fact, the locus 



ZO SO -i-O 



Temperatu-re 



5-6 



IT'corxentratiart.s varying between 10 5 §-\6 



of the maxima of these curves is a straight line, the mathematical equation 

 of which is approximately 



y = 6-56a;- 200-44. 



The significance of this straight line is that it shows that the fall which 

 occurs in the optimum temperature of the ferment as the H + concentration 

 is increased — beyond its optimum value — is proportional to the fall in 

 activity (or disablement) which the ferment undergoes at the physical 

 optimum point. 



Fig. 2 further shows that the temperature of destruction of the enzyme 

 also depends on the hydrogen ion concentration of the medium ; the greater 



2 K 2 



