TABLE 3.

Internal acidification induced by l-malic acid uptake in S. pombe and S. cerevisiae V5 YEp MAE1^a

l-Malic acid concn (mM)	Intracellular pH
	S. pombe		S. cerevisiae
	External pH 3.5	External pH 5	External pH 3.5	External pH 5
0	6.0 ± 0.01	6.39 ± 0.07	6.54 ± 0.01	6.66 ± 0.05
1	5.96 ± 0.06	6.16 ± 0.03	6.59 ± 0.02	6.63 ± 0.03
10	5.54 ± 0.03	5.98 ± 0.02	6.52 ± 0.02	6.44 ± 0.03
20	5.38 ± 0.03	5.87 ± 0.03	6.60 ± 0.03	6.42 ± 0.02

^aIntracellular pH was evaluated after incubation of the cell suspensions for 5 min with unlabeled l-malic acid in 0.1 M K₂PO₄ buffer, pH 3.5 or 5, by measurement of the distribution of [¹⁴C]benzoic acid across the plasma membrane. Values are the means of at least four repeated experiments.