ENERGY SUPPLY OF THE CELL 129 



the temperature from 25 to 65°C., i.e. 40°C., would result in a rate 

 of enzyme action 1.26'' = 2.52 times as rapid. The same increase 

 in temperature would cause the rate of enzyme deterioration at 

 65°C. to be 6.364 = 1^540 times as high as at 25°C. Only 10.67% 

 of the enzyme would be left intact after half an hour's exposure to 

 65°C. The increased rate of enzyme action is of no avail at very 

 high temperatures because there is no longer any enzyme. At 

 45 and 55°C., where the enzyme destruction is not quite so rapid, 

 the result of the increased rate of action becomes very noticeable. 

 But as all enzyme is destroyed before all saUcin is decomposed, the 

 reaction never becomes complete. This is accomplished only at the 

 lowest temperatures. 



As a result of this interlinking of two opposite effects, 

 the optimum temperature of enzyme action is not 

 definite. At one-half hour, the salicin is most rapidly 

 decomposed at 55°C.; after two hours, 45°C. is plainly 

 the optimum; after ten hours, 35°C. shows the largest 

 amount of decomposed salicin; and after forty hours, 

 the lowest temperature appears to be the best. This is 

 also shown in Fig. 16. The heavy ascending line 

 indicates the optimal rate at different temperatures. 

 It is seen to shift towards the lowest temperature with 

 increasing time. This is a very characteristic property 

 of the Tammann principle. 



The high temperature coefficient of deterioration is the 

 cause of the thermolability of enzymes. For most 

 enzymes, this coefficient is still higher than with emulsin. 

 Arrhenius (1907) gives the following values for Qio: 



Table 23. — Temperature Coefficients of Enzymes 



Of enzyme 

 action 



Of enzyme 

 destruction 



Rennet. 

 Trypsin , 

 Pepsin . . 



Qio = 2.61 

 1.61 

 2.06 



Qio = 65.8 

 17.8 

 33.7 



