ZYMASE 493 



and Sandberg,* the role of the co-enzyme would appear to be 

 that of a hydrogen acceptor since aldehydes, ketonic acids, 4- 

 nitro-bodies and disulphides can act as co-enzymes ; he 

 suggests that the action of all such substances consists in 

 accepting the hydrogen from pyruvic aldehyde hydrate until 

 sufficient acetic aldehyde has been formed to act as the 

 hydrogen acceptor, thereby becoming reduced to ethyl alcohol. 

 Harden summarizes the position in stating that the effect of 

 the co-enzyme can be reproduced by the addition of sub- 

 stances which are able to yield aldehydes under the action 

 of the enzyme carboxylase, which acts according to the 

 equation — 



R CO COOH = R CHO + CO^ 



In this connection it is interesting to note that the co- 

 enzyme of yeast is also found in the hot-water extract of 

 animal muscle, especially frog's muscle, and of other tissues ; 

 it is also present in milk but is absent from serum. Meyerhof f 

 has also shown that the co-enzyme of yeast plays an essential 

 part in the respiration of muscle as well as in that of yeast. 



According to von Euler and Myrback,J the activity of the 

 co-enzyme can be increased by successive precipitation with 

 lead acetate and silico-tungstic acid. 



THE ISOLATION OF ZYMASE. 



The following is the method pursued by Buchner in isolat- 

 ing zymase from Saccharomyces. One kilogram of com- 

 pressed yeast is rhixed with 250 grams of the infusorial earth 

 known as kieselguhr and a quantity of fine quartz sand. The 

 mixture is ground in a mortar until the microscope shows the 

 majority of the yeast cells to be broken. To this paste-like 

 mixture are added lOO c.c. of water which is very thoroughly 

 stirred in ; the mass is then wrapped in a cloth, placed in a 

 press and gradually subjected to a very high pressure — - 

 Buchner used a pressure as high as 500 atmospheres — the 

 liquid extracted being collected in a glass vessel. The resi- 

 due is then removed from the press, broken up, and again 



* Neuberg and Sandberg : " Biochem. Zeit.," 1920, 109, 290. 

 t Meyerhof : " Zeit. physiol. Chem.," 1918, lOl, 165 ; 102, i. 

 X von Euler and Myrback : id., 1924, 139, 281. 



