The Role of Polyphosphates in the Transport Mechanism of Glucose in Yeast Cells

Abstract

Several cations inhibit anaerobic fermentation of glucose by intact yeast cells. Some ions (e.g. Hg + + ) penetrate into the cytoplasm and cause an irreversible inhibition of fermentation. Other ions (e.g. UO ++ , Ni + + , and Co + + ) are reversibly bound to a substance at the outside of the yeast cell identified as polyphosphate. Although the cations are bound to exactly the same extent, their influences on fermentation differ greatly. Thorium ions are bound not only to the polyphosphates, but in addition, to phosphatides in the cell membrane. Under circumstances in which glucose is transported into the cell, the amount of polyphosphate in the outer face of the membrane decreases considerably. If yeast is poisoned with monoiodoacetate, the number of glucose molecules that can still be taken up equals the original number of cationbinding sites at the outer surface of the membrane. These data suggest that one molecule of glucose is taken up in connection with the disappearance of one polyphosphate monomer. The hypothesis is framed that the uptake of glucose into the yeast cell is associated with an enzymic phosphorylation (possibly of the carrier), with polyphosphate as phosphate donor. The inhibition of glucose uptake caused by certain metal ions may be the consequence of induced changes in the spatial arrangement of polyphosphate chains; the greater the change in configuration, the larger is the inhibition.

POLYPHOSPHATE FORMATION IN THE ROOTS OF DESCHAMPSIA FLEXUOSA AND URTICA DIOICA

“…These proportions compared with that reported for Banksia ornata (30%), or a value of 20% reported for yeast (van Steveninck and Booij, 1964), do not seem to be of great significance.…”

Efeitos do cádmio sobre o crescimento das leveduras Saccharomyces cerevisiae PE-2 e Saccharomyces cerevisiae IZ-1904, e a capacidade da vinhaça em atenuar a toxicidade

“…Como estes polifosfatos atuam no transporte de glicose para dentro da célula [11,22,37,40,41] este transporte deve ter sido completamente inibido nesta concentração de cádmio (0,5mM). Provavelmente as leveduras se encontram em um estado de semi-letargia, não sendo capazes de metabolizar a glicose do meio de fermentação, utilizando para sobreviver as suas reservas endógenas (nitrogênio, trealose e glicogênio).…”

Effects of nickel on the mineral composition of Fleischmann’s yeast (Saccharomyces cerevisiae)

“…The slowest fermentation rate (Figures 3 and 4) and lowest viability rate (Figure 12) in the presence of nickel and low pH can be explained by the decrease in sugar absorption by yeast cells, due to the complexation of the phosphate groups of the plasmatic membrane by nickel, as proposed by VAN-STEVENINCK 42 and VAN-STEVENINCK e BOOIJ 43 .…”

“…Heavy metals may also affect the sugar entering the yeast cell when they are linked to the anionic bindings of the plasmatic membrane. Several authors 31,42,43 have reported that sugar transport into the yeast cell is inhibited by heavy metals and this inhibition may be involved in these metals' (e.g., nickel, cobalt and cadmium) interaction with the polyphosphate membrane, causing a conformational change in some active sites, which would render binding with the sugar unviable.…”