266 BACTERIOLOGICAL CHEMISTRY 



(2) to proceed at such a rate that inorganic phosphate is 

 supplied sufficiently rapidly to enable the reactions of 

 equation (1) to proceed at their maximum velocity. 



No such acceleration of fermentation occurs on the 

 addition of inorganic phosphate or arsenate to living 

 yeast fermentations, which proceed about twenty to 

 forty times as fast as those due to yeast preparations. 

 The addition of inorganic phosphate to the latter increases 

 the velocity some ten to twenty times. Presumably in 

 living yeast cells the ratio of the activities of the enzymes 

 is at an optimum, and the balance is upset during the 

 extraction of the yeast juice or other treatment. Harden 

 showed that the velocity of fermentation decreased and 

 the magnitude of the response to added phosphate 

 increased, with greater disintegration of the cell structure. 



From calculations based on the phosphorus content of 

 the yeast cell it appears that the phosphate -ester cycle 

 must be completed once every five or six minutes in 

 order to maintain the normal rate of fermentation. 

 For an average yeast preparation the cycle takes 

 approximately two hours. 



Harden and Young showed that the ester which 

 accumulated after addition of inorganic phosphate was a 

 hexose diphosphate, later shown to be 1 : 6-fructose 

 diphosphate, even when the sugar being fermented is 

 glucose or mannose. Later, Robison isolated a hexose 

 monophosphate from such solutions, which was ultimately 

 proved to be a mixture of about 80 per cent, of 6-glucose 

 monophosphate (loiown as Robison's ester) and 20 per 

 cent, of 6-fructose monophosphate. More recently 

 Embden and Myerhof and their co-workers have isolated 

 a number of triose monophosphates, including a-glycero- 

 phosphoric acid, 2- and 3-phosphoglyceric acids and 

 2-phosphopyruvic acid, from alcoholic fermentations. 

 Tiieir importance will be seen at a later stage. 



