INVERTASE. 519 



exceeding 57C. In the absence of a polarimeter, the test may be 

 performed as follows : 5 c.c. of Fehling solution are boiled with 

 i c.c. of test liquid (40 c.c. of beer and 40 c.c. of saccharose 

 solution, after digestion for twenty-four hours). If the liquid 

 remain blue, with a slight red precipitate, no invertase is present ; 

 in the opposite event the Fehling solution will be reduced com- 

 pletely. 



Enzymatic action is also greatly influenced by temperature in 

 the case of invertase ; and whilst this action begins at about 

 zero C., the optimum temperature is considerably higher. In the 

 case of invertase from top-fermentation pressed yeast, A. MAYER 

 (XI.) found this optimum temperature at 31 to over 36 C., and 

 44-48 C. in that from bottom-fermentation yeast. On the other 

 hand, according to KJELDAHL (I.), the optimum temperature for 

 the activity of invertase from bottom yeast is 52.5 C., and that for 

 the enzyme from top yeast, 56 C. A. MAYER (XI.) considers 

 that these divergencies are explained, on the one hand by the 

 invertase preparations being injured in the course of production, 

 e.g., by treatment with alcohol, and, on the other hand, by the 

 fact that adherent impurities have a stimulating or restrictive 

 influence on the enzymatic action according to their character. 

 After very careful investigation O'SuLLivAN and TOMPSON (I.) 

 determined the optimum temperature at 55-60 0. A consider- 

 able difference also exists in the reports as to the temperature at 

 which this enzyme is destroyed, the explanation being the same as 

 just given. For instance, alcohol lowers the destruction tempera- 

 ture, whereas high concentration and the presence of glycerine has 

 the opposite effect. Prolonged exposure to a constant temperature 

 also has an injurious effect, A. MAYER (XII.), for instance, finding 

 the enzyme to be destroyed at 51 C. in some cases, whereas in 

 others it remained active, though weak, at 65 and even at 

 66 C. According to O'SULLIVAN and TOMPSON (I.), the destruc- 

 tion temperature of invertase is 75 C. ; and the same result was 

 obtained by BAU (XXVI.), who did not prepare the enzyme in a 

 pure state, but examined it direct in the cell by the BOKORNY (IV.) 

 method. This method obviates the injury always suffered by the 

 enzyme in the course of isolation ; but, on the other hand, allow- 

 ance must be made for the fact that, when the experiment is 

 repeated, the yeast may not be in the same physiological condition 

 in all the tests. It is true that the conditions of nutrition of the 

 yeast do not modify the properties of the enzyme ; but its 

 quantity and activity may be influenced by the accumulation or 

 diminution of other substances present in the yeast cells. From 

 additional experiments made, it may be assumed that yeast 

 invertase, provided it has remained uninjured, will develop its 

 maximum activity at 52-56 C., and that it is certainly destroyed 

 in aqueous solutions, and also in the yeast cell, by a temperature 

 of 75 C. In an absolutely dry state it will stand far higher 



