418 



The Action of Enzymes on Hexosephosphate. 

 By Victor J. Harding. 



(Communicated by A. Harden, F.K.S. Eeceived May 21, — Eead June 20, 1912.) 



(Biochemical Department of the Lister Institute.) 



According to the theory advanced by Harden and Young,* the presence of 

 phosphate is essential for the alcoholic fermentation of sugar by yeast-juice. 

 In the presence of the fermenting complex, the phosphate and sugar react 

 together, with the simultaneous production of equivalent quantities of 

 carbon dioxide, alcohol, and hexosephosphate. The hexosephosphate is then 

 hydrolysed by an enzyme present in yeast-juice, with formation of a hexose 

 and free phosphate, and the latter then again undergoes the first reaction 

 with more sugar. The phosphate thus repeatedly passes through a cycle 

 which may be represented by the following equations : — 



(1) 2C 6 H 12 6 + 2E 2 HP0 4 = 2C0 2 + 2C 2 H 6 + C 6 H 10 O4(PO 4 E 2 ) 2 + 2H 2 0, 



(2) C 6 H 1( A(PO-4E 2 ) 2 + 2H 2 = C 6 H 12 6 + 2E 2 HP0 4 . 



The normal rate of fermentation of excess of sugar by active yeast-juice is 

 therefore dependent upon the rate at which phosphate is set free from the 

 hexosephosphate, and any acceleration of this reaction would increase the 

 rate of fermentation of the sugar. Thus the addition to yeast-juice and 

 sugar of a hexosephosphatase, that is, an enzyme capable of hydrolysing 

 hexosephosphate, would be expected to bring about this result, and the 

 following experiments on the action of various enzyme preparations on 

 sodium hexosephosphate have been carried out primarily with the object of 

 finding such an enzyme. 



As a result, it was found that enzymes of very different origin (Eicinus 

 lipase and almond emulsin) were capable of hydrolysing hexosephosphate, 

 but the effect of adding these to fermenting yeast-juice has not yet been 

 ascertained. 



Preparation of Hexosephosphoric Acid. — The solution of hexosephosphoric 

 acid used in these experiments was prepared as described by Young,t by 

 decomposing the lead salt with hydrogen sulphide. The solution of free 

 hexosephosphoric acid was made neutral to litmus by a known volume of 

 sodium hydrate solution, and such a neutral solution was used in all the 

 experiments. The amount of hexosephosphoric acid was previously deter- 



* 'Boy. Soc. Proc.,' 1908, B, vol. 80, p. 299. 



t ' Boy. Soc. Broc.,' 1909, B, vol. 81, p. 531. 



