Studies on the Enzyme-Action of Yeast.

Abstract

If a suspension of yeast is brought together with a solution of glucose in adequately chosen proportions, then some protein admixed, and precipitated by a suitable protein precipitant, the glucose is carried down with the protein and yeast, and no trace of glucose can be recovered in the filtrate.

If, for example, 50 cc. of a 0.2 to 0.4 per cent solution of glucose and 10 g. of yeast, suspended in 50 cc. of diluted egg white or neutral casein solution, are poured together and mixed, subsequent precipitation by tungstic acid will remove all the glucose from solution. And this reaction takes place, even though fermentation be prevented by chilling both the yeast and the glucose to 0° C. before they are united, and kept at that temperature throughout the entire operation. Evidently an adsorption-like combination takes place between yeast and glucose as soon as they come into contact.

If the yeast is separated from a yeast-glucose solution by centrifugation or filtration, the glucose is recovered in the solution. On dialysis the glucose passes through the membrane. These observations indicate that the union between yeast and glucose is so labile that it cannot withstand the disrupting forces involved in these operations, and even might cast doubt on the conception of a union between yeast and glucose.

But on our further inquiry into the nature of the initial yeast-glucose combination, it was founcl that factors which damage enzyme action invariably also destroy or prevent the formation of this combination. Thus, in the presence of phenol, sodium fluoride, salycylic acid, etc., which prevent fermentation, the glucose is not removed from solution with the yeast-protein precipitate. Heating of the yeast-glucose mixture, too, prevents the precipitation of glucose.