502 POPULAR SCIENCE MONTHLY. 



The alcoholic enzyme. The enzyme that converts sugar into alcohol 

 and carbon dioxide has been only recently discovered, although it has 

 been diligently sought for since the time of Pasteur. The discovery 

 of Buchner in 1896 that, by applying great pressure to a mass of yeast 

 cells, an enzyme, which he named zymase, could be extracted gave in 

 fact a new impulse to all enzyme study. Zymase appears to dislocate 

 the sugar molecule according to the classic formula : 



CaHi^Oe — 2C2H5OH + 2CO2 

 dextrose alcohol carbon dioxide 



180 gr. 92 gr. 88 gr. 



The explanation of the prolonged failure of investigators to dis- 

 cover zymase lies in the fact that this enzyme is closely associated with 

 the substance of the living yeast cell and does not diffuse out into the 

 surrounding medium as does another common yeast enz}T2ie already 

 mentioned under the name of invert-ferment or sucrase. In solution, 

 zTma&e quickly loses its strength, probably partly because of oxidation, 

 partly because of the destructive action of the tryptic enzymes of yeast. 

 Zymase is able to convert a number of different sugars into alcohol and 

 carbon dioxide: maltose and sucrose are readily fermentable, galactose 

 much less readily and lactose not at all. Glycogen can be slowly fer- 

 mented by zymase, but is not fermented by the living yeast cell because 

 it can not pass through the cell-membrane into the cell and zymase 

 can not pass out. The brilliant researches of Emil Fischer upon the 

 relation of the configuration of the eugar molecule to its f ermentability 

 have demonstrated how delicate is the relation obtaining between the 

 structure of the sugar molecule and the enzyme that attacks it. A 

 slight rearrangement in the position of the atoms within the molecule, 

 the actual number of atoms remaining all the while the same, is suffi- 

 cient to determine whether a sugar can be fermented or not. Only in 

 those cases where the geometrical build of the enzyme conforms to that 

 of the sugar molecule can fermentation occur. To use Fischer's meta- 

 phor, the enzyme must fit the substance it attacks as closely as the right 

 key fits the wards of the lock that it opens. 



Other enzymes. A few other important enzymes can be but briefly 

 mentioned, since the limits of this review do not permit of a fuller con- 

 sideration. A group of enzymes of which emulsin is the type may be 

 classed as the glucoside-splitting enzymes. These ferments are able to 

 split up glucosides — which may be described as compounds of glucose 

 (or some other sugar) with an alcohol, ether, aldehyde, or similar 

 body — into glucose and the aldehyde or other associated compound. 

 Emulsin is found in many plant tissues, but it is doubtful if it occurs 

 in any animal body. The physiological role of emulsin is not wholly 

 understood ; it is possible that the glucose formed by the enzyme action 

 is useful in the nutrition of the plant, or it may be true that the toxic 



