TABLE 1.
Transmembrane gradients of l-malic acid concentrations after dilution of preloaded cellsa
| l-Malic acid form | 2 mM
|
10 mM, pH 4d
|
||||
|---|---|---|---|---|---|---|
| pH 3.5b
|
pH 6c
|
|||||
| IC | EC | IC | EC | IC | EC | |
| Dianionic | 9.04 | 0 | 9.04 | 0.18 | 13.9 | 0.06 |
| Monoanionic | 0.36 | 0.11 | 0.36 | 0.02 | 0.55 | 0.75 |
| Undissociated | 0 | 0.09 | 0 | 0 | 0 | 0.19 |
a
S. cerevisiae V5 YEp MAE1 cells, preloaded by incubation for 30 min with 2 or 10 mM labeled l-malic acid (specific activity, 10 × 105 or 2 × 105 dpm/μmol, respectively) were diluted with 2 ml of 0.1 M potassium phosphate buffer at the indicated pH. Intracellular and extracellular l-malic acid concentrations (IC and EC, respectively) were determined immediately after dilution. Values are in millimolar units.
b
Fig. 3, line C.
c
Fig. 3, line D.
d
Fig. 3, line B.