Mechanism of benzoic acid uptake by Saccharomyces cerevisiae

A fast uptake of the preservative benzoic acid was observed in Saccharomyces cerevisiae, reaching saturation in about two min and then remaining constant at this level. The strong dependence of benzoic acid uptake on pH was due to the relative distribution of molecular and ionic forms in solution and not to the pH itself. The molecular form was the only one taken up by the cells. The specificity of the uptake mechanism was evidenced by the pattern of irreversible heat inactivation of the uptake system resembling protein denaturation by heat. Furthermore, the effect of temperature on the uptake was similar to that observed in enzymic reactions, whereas the kinetic data of uptake conformed to the Michaelis-Menten curve of saturation with a Km of 1.54 X 10(-2) M and Vmax of 3 X 10(-3) M/10s. The evidence presented in this paper indicates that compounds of protein nature are involved in the uptake of this preservative.