PROPERTIES OF BUCHNER'S ZYMASE 93 



The investigations of Buchner and his collaborators have revealed 

 the presence of a substance in boiled juice which protected the zymase 

 from the action of the endotryptase. This has received the name an- 

 tiprotease. This enzyme protects gelatin and milk, also, from the 

 action of the endotryptase in yeast juice. It prevents the liquefac- 

 tion of milk and the peptonization of gelatin. 



The existence of this antiprotease permits an explanation of how 

 the fermenting action is preserved for many days when boiled juice is 

 added to fresh juice; otherwise it would disappear rapidly. In the 

 yeast juice, without the addition of the boiled juice, an almost complete 

 disappearance of protein substances was noticed after 7 days. When 

 boiled juice is added no precipitation of protein occurs. The addi- 

 tion of the boiled juice seems, then, to protect the fresh juice for a 

 period of time against the proteolytic action of the endotryptase. 

 The experiments of Buchner indicate that it will protect also from the 

 action of pepsin and trypsin. This proves, then, that zymase is a 

 protein substance. Careful experiments have indicated that it is 

 possible to destroy the coferment of boiled juice without destroying 

 the antiprotease. This may be accomplished by heating it for several 

 hours. The juice thus treated still exerts a protective action towards 

 gelatin and yeast juice. It contains, then, an antiprotease. On the 

 contrary, this juice is not capable of regenerating the preserved yeast 

 juice because it contains no coenzyme. The antiprotease is, then, dis- 

 tinct from the coenzyme. It does, however, have some likenesses 

 to the latter; it is destroyed by lipase and seems to be a saponifiable 

 ether of phosphoric acid. The antiprotease seems to play an impor- 

 tant role in the life of the yeast and regulates its digestive functions 

 (especially autolysis) . 



Zymase acts best in an alkalin medium. The addition of sodium 

 carbonate and phosphate exerts a favorable action. It is destroyed by 

 heating to 55; in the dry condition, if desiccation has been carried 

 out in vacuo at 40, it is able to resist 140. Temperature exerts a 

 decided influence on the activity of zymase because the action of endo- 

 tryptase and lipase on it is much altered with the temperature. That 

 temperature at which zymase exerts the greatest fermenting action is 

 about 14. The optimum temperature seems to be higher; but endo- 

 tryptase will attack zymase when the temperature is even higher. 



Concentration plays a role in the activity of zymase. Fermenta- 

 tion increases with the concentration of the sugar; this explains the 

 relation of concentrated sugar solutions (15 per cent) to the suppres- 

 sion of endotryptic action. The optimum concentration of sugar 

 seems to be about 25 per cent. 



The yeast juice contains, as we have said, hydrolytic enzymes for 



