PROPERTIES OF BUCHNER'S ZYMASE 91 



to note that the quantity of zymase in pressed yeast increases con- 

 siderably when the yeast is kept at low temperatures and that it 

 diminishes in yeast during the course of fermentation. The investi- 

 gations of Haydruck and Delbruck have shown that yeasts cultivated 

 in a solution of sugars and mineral salts and removed at the moment 

 when fermentation is most active, does not contain much zymase. If, 

 on the contrary, a yeast is taken from a vigorous fermentation, 

 washed, and kept at a low temperature, the zymase content increases 

 rapidly. (Delbruck, Buchner, and Spitta.) All this seems to be ex- 

 plained by the fact that endotryptase and lipase find themselves 

 affected by the low temperature and do not act on the zymase which 

 they destroy under other conditions. 



In the refrigerator zymase is kept with difficulty and soon loses 

 its activity at the end of one or two days when placed at ordinary 

 temperatures. At low temperatures, it is destroyed by degrees. 

 This destruction was at first explained by thinking that zymase was 

 easily oxidized by air. The investigations of Buchner and Antoni l 

 have, on the contrary, indicated that oxygen has no action on zymase 

 either during periods of its conservation or active fermentation, 

 as they determined it. Its alteration arises from the endotryptase 

 which is associated with it and perhaps to the lipase which one also 

 finds in the juice. The work of Gromow and Grigoriew indicates that 

 endotryptase attacks and digests it. On the other hand, the results 

 secured by Harden, Buchner, Wroblewsky seem to indicate that lipase 

 acts on the coferment. One is able, however, to keep yeast juice in 

 all its activity by drying it in a vacuum at 35 C. The juice is then 

 changed to a yellow which may be kept for a long time unaltered (10 

 or 12 months). Zymase also retains its activity for a long time if 

 preserved in a 15 per cent solution of saccharose, this concentration 

 acting on the endotryptase. 



The investigations of the two English investigators, Harden and 

 Young, have widened the horizon of our knowledge with regard to 

 the constitution of zymase. They have shown that when yeast juice 

 is introduced into a dialyzing apparatus, it may be divided into two 

 parts, a non-dialyzable residue and a liquid which does dialyze. The 

 residue is without fermenting activity and has been given the 

 name of "inactive residue." The dialyzable liquid, which is without 

 action on sugar, has been regarded as a coferment. Fermentation is 

 only produced when the two parts are reunited. The inactive resi- 

 due may also be regenerated by adding yeast juice which has been 

 submitted to boiling, which indicates that the coferment is able to re- 



1 Buchner, E. and Antoni, W. Weitere Versuche iiber die zellfreie Garung. 

 Zeit. phys. Chem. 44, 1905. 



