Effect of sulfite or nitrite on the ATP content and the carbohydrate metabolism in yeast

Low concentrations of sulfite or nitrite (about 0.5 mmol) when applied at pH 3.6, caused a rapid and drastic decrease of the concentration of ATP in yeast cells. Under these conditions, alcoholic fermentation was inhibited by sulfite and to a lesser extent by nitrite. Ethanol consumption under aerobic conditions was shown to be more sensitive to nitrite than to sulfite. This indicates a higher sensitivity of respiratory processes to nitrite than to sulfite. Among 15 enzyme activities assayed in extracts from yeast cells after incubation with sulfite or nitrite, glyceraldehyde-3-phosphate dehydrogenase was shown to be the most sensitive. Analysis of the steady-state concentrations of intermediates of alcoholic fermentation in intact yeast cells also implies inhibition by sulfite or nitrite of the glyceraldehyde-3-phosphate dehydrogenase step of fermentation. In contrast to nitrite, sulfite had an additional effect by accumulating the intracellular steady state concentration of glyceraldehyde-3-phosphate 10 to 100-fold over the concentration in the absence of sulfite. In vitro studies on the equilibrium catalyzed by triosephosphate isomerase or aldolase confirmed the postulated shift of equilibrium concentrations by a formation of complex of glyceraldehyde-3-phosphate with sulfite.