Surface Tension and Ferment Action. 



577 



Since in all the following experiments relatively small concentrations of 

 invertase were used, so that the process of inversion was slow, the effect of 

 the mutarotation of glucose did not affect the readings. This was verified by 

 special control experiments in which dilute sodium carbonate was added to 

 the solution before the readings were taken. 



The retarding effect of surface tension was confirmed in a number of other 

 experiments. It is not necessary to quote these experiments in detail, as the 

 effect is evident in the experiments given below which deal with the further 

 analysis of the phenomenon. 



In the action of an enzyme on a substrate one may distinguish two separate 

 phases : firstly, the combination of the enzyme and the substrate, and, secondly, 

 the chemical change which proceeds in this compound of enzyme and 

 substrate. A priori surface tension may have an effect either on the first 

 phase or on the second phase or on both. 



We will consider first the possibility of surface tension action on the second 

 phase of enzyme action. Just as the catalytic action of an enzyme has been 

 likened to a lubricant producing its action by diminishing friction, so the 

 effect of surface tension might be like that of a brake, retarding the process 

 by increasing the friction. If that were so, one would expect to find that 

 retardation disappears when the brake is removed, i.e. when surface energy is 

 reduced to the dimensions which obtain in the control. To test this point a 

 number of test-tubes filled with beads were charged with the mixture of 

 substrate and ferment. After a given number of hours, when a distinct 

 inhibition had become noticeable, the fluid (or part of it) was removed from 

 one of the test-tubes filled with beads, and inversion allowed to proceed as 

 usual in a test-tube without bead's. An example will make the arrangement 

 clear. 



Experiment B. 22.6.14. Invertase D, 18.5.17, 10 per cent. 



2*5 c.c. invertase and 100 c.c. sucrose, 20 per cent. Temperature of 



digestion 27°. 



Without Beads. With Beads. ' 



Hours. f » — — v t " 



Control tube. Tube 1a. Tube 2a. Tube 3a. Tube 1. Tube 2. Tube 3. Tube 4. 



+12-90 +12-90 +12 90 +12-90 +12-90 



10 +12-14 + 12-59 — — ' — 



24 +11-37 +11-80 j +11-88 — — 



49 +9-26 +10-25 +10-42 j +10-57 — 



98 +5-80 +7-66 +7-75 +8-08 +8-47 



In this particular experiment the inhibition disappeared only partially after 

 reducing the surface energy. It is still evident after the removal of beads, 



