126 PHYSIOLOGICAL CHEMISTRY. 



Invertase or Sucrase. One of the most common and im- 

 portant of these enzymic reactions is the inversion of cane 

 sugar, forming glucose and fructose. 



CuHaOn + H 2 O = C 6 H 12 O 6 + C 6 H 12 O 6 . 

 Glucose Fructose 



The name invertin or invertase has been given to the enzyme 

 which accomplishes this, but sucrase would be in better accord 

 with the general nomenclature. The presence of this invert- 

 ing ferment in many kinds of yeast has been long known. 

 The yeast cell alone is not able to convert cane sugar into alco- 

 hol and carbon dioxide; an inversion must first be brought 

 about in some manner. In old yeast or in yeast in which the 

 cell has been destroyed by heat or by mechanical means the 

 inverting enzyme seems to be present in greatest abundance. 



Invertase is found in various animal secretions, especially in 

 the intestinal juice. The inverting power of this secretion is 

 marked, while with the pancreatic secretion the inverting 

 power is much less pronounced. In the gastric juice the in- 

 verting enzyme is said to be present in some amount and is 

 sufficient to change part of the cane sugar of the food inde- 

 pendently of the acid likewise present. 



The blood does not appear to contain this invertase, since a 

 solution of cane sugar injected into the veins is eliminated 

 later by the kidneys unchanged. If injected into the portal 

 vein, and thus made to pass the liver, inversion takes place 

 rapidly, as that organ possesses the enzyme in quantity. 



Many of the higher as well as the lower plant organisms 

 contain invertase, which accounts for the change of the cane 

 sugar into invert sugar in certain cases. In general this reac- 

 tion may be easily followed by the polariscope, as the strong 

 dextro-rotation of cane sugar gives place to the levo-rotation 

 of invert sugar. It is possible to make a fairly pure invertase 

 solution from some kinds of yeast, and such a solution has 

 certain practical applications in analytical investigations. By 

 extracting yeast with thymolized water a solution is obtained 

 which rapidly inverts cane sugar, but which is practically with- 



