252 



Mr. A. Compton. Optimum Temperature of 



That the curves might be vertical enough to give sharply defined 

 maximum points, it was decided to aim at obtaining about 70 per cent, 

 hydrolysis of the substrate at the optimum temperature. A cursory 

 examination of fig. 3, which was constructed at approximately + 34°, shows 

 that to obtain such curves — assuming for the moment, what fig. 4 already 

 indicates the probability of, that the optimum temperature is independent 

 of the concentration of the substrate, and situated at about + 34° — the 

 quantities of enzyme required, in actions of 15 hours' duration, are 1/55, 

 1*35, T30, T70 and 2 - 50 mgrm. respectively for the concentrations M/5, 

 M/10, M/15, M/30 and M/50 of the substrate. Working with these 

 quantities the experimental data obtained are set forth in Table V. 



By plotting as before the percentage of salicin hydrolysed against the 

 temperature of the experiment the foregoing numbers give the curves repre- 

 sented in figs. 5, 6, 7, 8 and 9. 



On careful examination the curves below all show that the activity of the 

 enzyme is greatest between +33 - 5° and +34*5°; in other words, that the 

 optimum temperature is about + 34°, and is constant, notwithstanding the 

 wide variations in the dilution of the substrate and the accompanying 

 variations in the dilution of the enzyme. 



