Salicin Hydrolysis by Enzyme Action. 



247 



If the percentages of salicin hydrolysed be plotted as ordinates and the 

 quantities of enzyme as abscissae these numbers give the activity curve 

 shown in fig. 1. 



The preliminary determination of the optimum temperature of the 

 enzyme, the second stage of the inquiry, was carried out as follows : A 

 solution of the enzyme was prepared containing 10 times the quantity of 



ioo_ 



60° c. 



10 2-0 3-0 4-0 SO 6-0 7-0 3-0 9 ma. 



Quantity of enzyme in millij]ra.ms. 5> 



Fij.l 



enzyme necessary to produce the percentage of hydrolysis decided upon — 

 in this case 0'9 mgrm. for a 50 per cent, hydrolysis as shown by fig. 1 — 

 dissolved in 10 cm. 3 of redistilled water. After half to one hour of contact 

 at the ordinary temperature the solution was introduced in portions of 

 1 cm. 3 into each of a series of eight or nine test-tubes already containing 

 286 mgrm. of salicin and 4 cm. 3 of water. The tubes were then plunged 

 into water-baths kept at known temperatures, and after 15 hours the 

 action was stopped and the proportion of glucoside hydrolysed determined as 

 before. The numbers obtained are set forth in Table II. 



By plotting the percentage of salicin hydrolysed against the mean 

 temperature of the experiment these numbers give the curve indicated above 

 in fig. 2. The optimum temperature under the foregoing conditions is thus 

 found to be + 34°. 



