Abstract
It was shown earlier(1) that 2-deoxy-D-glucose (2DG) elicits a dissimilation of glycogen in yeast, with one mole of CO2 formed for each glucose equivalent of glycogen lost. These data were consistent with a proposed mechanism of cyclic fermentation reported earlier(2) from studies made on dialyzed yeast extracts. In the present paper certain characteristics of the 2DG-stimulated fermentation in cells are presented along with possible implications of such findings.
Methods. All experiments were done at 30°C under nitrogen on nonproliferating baker' yeast previously washed and aerated(3). Tris-succinate-tartrate adjusted to appropriate pH served as buffer. CO2 production was measured in a Warburg apparatus. Glycogen was determined using the method of Berke and Rothstein(4) after washing the yeast 3 times with distilled water.
Results. Specificity of the stimulatory effect of 2DG; absence of effects of KCl. In Fig. 1 and Table I are shown cumulative CO2 productions by yeast suspensions for various sugars added under anaerobic conditions. As reported by Brady et al(5) and later, by us (1), it is seen that a low but significant rate of endogenous fermentation occurred. Addition of 2DG at pH 5.7 resulted in a rate of CO2 production about 4.5 times that of the endogenous control. This phenomenon had been reported earlier(1). On the other hand, KCl, 3-0-methyl-D-glyeopyranose, L-(-)rhamnose, d-sorbitol and galactose yielded rates not appreciably different from the endogenous rate (CO2 formed in the presence of 3-0-methyl glucose, sorbitol and galactose were not included in Fig. 1 to maintain clarity. Actual values for CO2 produced in 130 minutes lie between those in the presence of KCl and rhamnose.) Results with L-sorbose were equivocal. In contrast to the results obtained in the presence of acetic acid(7), KCl had no effect on either endogenous (Fig. 1) or 2DG-induced anaerobic CO2 production (Table I), at pH 5.7.
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