L-malic-acid permeation in resting cells of anaerobically grown Saccharomyces cerevisiae.

The study of permeation of L-malic acid in cells of Saccharomyces cerevisiae at pH 3.0 was carried out with (U-14C)-labelled L-malic acid. Resting cells were used in these experiments. They were previously anaerobically grown on glucose. This study showed that this transport is the result of two competitive mechanisms, one for the uptake and one for the efflux. The uptake mechanism seems to be a simple diffusion of the L-malic acid in a non-dissociated form. The efflux mechanism seems to be an active transport of L-malic acid that is very dependent on the temperature. At the steady state, the result of uptake and efflux mechanisms leads to an intracellular concentration which is twice or three times the extracellular concentration.