378 ENZYMES 



The names of Harden and Young particularly are associated 

 with the problem, and a brief account of their work may be 

 given.* 



The alcoholic fermentation of glucose by yeast-extract is 

 greatly increased by the addition to the fermenting liquor 

 of yeast-juice, which has been boiled so that all enzymes 

 are destroyed and filtered. After such addition, there is to 

 begin with a greater evolution of carbon dioxide, which gradu- 

 ally diminishes to a rate which remains practically constant 

 for several hours and usually is about equal to that given 

 by an equal volume of the same yeast-extract and glucose to 

 which boiled and filtered extract has not been added ; but the 

 diminution in the fermentation rate is slower than in the con- 

 trol, so that fermentation continues for a longer period, the 

 extra amount of carbon dioxide evolved being directly pro- 

 portional to the volume of boiled juice added. The accelerat- 

 ing factor is a phosphate, and analysis showed that the extra 

 quantity of carbon dioxide evolved in the initial period of high 

 evolution, when a phosphate or boiled extract is added, corre- 

 sponds to the evolution of one molecular proportion of carbon 

 dioxide for each atom of phosphorus added in the shape of 

 phosphate. It should thus be possible to separate yeast-juice 

 into two complementary parts, either one of which depends 

 upon the presence of the other in order that fermentation may 

 take place. This was accomplished by filtering the expressed 

 yeast-juice through a Martin gelatine filter under a pressure of 

 50 atmospheres. The residue remaining in the candle is in- 

 active^ and so also is the filtrate which contains the active 

 principle, which is neither destroyed by heat nor precipitated 

 by ammoniacal magnesia mixture. This activating substance, 

 or co-ferment, is a salt of hexose phosphoric acid. 



The alcoholic fermentation of glucose therefore takes place 



* Harden and Young: " Proc. Roy. Soc., Lond.," B., 1906, 77, 405; 1906, 

 73, 369 ; 1908, 80, 299 ; 1909, 8l, 336 ; 1910, 82, 321 ; 1911, 83, 451 ; " Centrlbl. 

 Bakt.," 1910, 26, 178. Young : " Proc. Roy. Soc., Lond.," B., 1909, 8l, 523 ; 

 " Biochem. Zeit.," 1911, 32, 177. 



f- The aqueous solution of the residue does not keep for long ; it may, how- 

 ever, be preserved for some time by spreading it out on a clock glass and placing 

 in a sulphuric acid desiccator. It dries to a brown, brittle substance which can 

 easily be ground to a powder. In order to purify, the powder may be dissolved 

 in water and once more filtered and dried as before. 



