Interaction of phosphate with monovalent cation uptake in yeast.
The uptake of monovalent cations by yeast via the monovalent cation uptake mechanism is inhibited by phosphate. The inhibition of Rb+ uptake shows saturation kinetics and the phosphate concentration at which half-maximal inhibition is observed is equal to the Km of phosphate for the sodium-independent phosphate uptake mechanism. The kinetic coefficients of Rb+ and TI+ uptake are affected by phosphate: the maximal rate of uptake is decreased and the apparent affinity constants for the translocation sites are increased. In the case of Na+ uptake, the inhibition by phosphate may be partly or completely compensated by stimulation of Na+ uptake via a sodium-phosphate cotransport mechanism. Phosphate effects a transient stimulation of the efflux of the lipophilic cation dibenzyldimethylammonium from preloaded yeast cells and a transient inhibition of dibenzyldimethylammonium uptake. Possibly, the inhibition of monovalent cation uptake in yeast can be explained by a transient depolarization of the cell membrane by phosphate.
D000693:Anaerobiosis; D001692:Biological Transport / Q000187:drug effects; D002414:Cations, Monovalent; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010710:Phosphates / Q000378:metabolism / Q000494:pharmacology*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012413:Rubidium / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D013793:Thallium / Q000378:metabolism
D002414:Cations, Monovalent; D010710:Phosphates; D000644:Quaternary Ammonium Compounds; D012964:Sodium; D013793:Thallium; D012413:Rubidium