Accumulation of nitrite and sulfite in yeast cells and synergistic depletion of the intracellular ATP content.

When nitrite or sulfite are applied to yeast cells below pH 5.0, an enormous intracellular accumulation occurs. It is assumed that nitrite and sulfite penetrate the cell membrane in their undissociated forms as nitrous acid (pK = 3.3) or sulfurous acid (pK = 1.8), respectively. Due to the neutral intracellular pH they are trapped inside the cell in their anionic forms, which are impermeable to the cell membrane. It has previously been shown that sulfite causes a rapid depletion of the ATP content of yeast cells [Schimz, K.L. and Holzer, H. (1979) resp. Hinze et al. as above]. Similarly, millimolar concentrations of nitrite decrease the ATP level to less than 10% of the initial value. Nitrite and sulfite in combination deplete the ATP content of yeast cells much stronger than expected for the sum of the separate effects of these compounds ("synergistic effect").