TABLE 1.

Influence of unlabeled carbon sources on [¹⁴C]succinate transport^a

Competitive substrate	Growth of P. lemoignei on substrate	pKa1	pKa2	pKa3	Inhibition of succinate uptake (%)
Dicarboxylates
None					0
Succinate	+	4.17	5.64		80
d,l-Malate	±	3.42	5.10		20
Fumarate	−	3.00	4.50		25
Maleate	−	1.90	6.50		97
Monocarboxylates
Acetate	+	4.76			90
Propionate	±	4.88			95
Lactic acid	−	3.87			90
Pyruvate	+	2.49			90
Butyric acid	+	4.82			95
4-Hydroxybutyric acid	+				90
3-Hydroxybutyrate	+	4.29			90
Valerate	+	4.81			90
Octanoate	−	4.85			95
Tricarboxylate (citrate)	±	3.13	4.80	6.39	25
Amino acids
l-Alanine	−	2.34	9.69		40
l-Aspartate	−	1.88	3.86	9.82	<2
l-Glutamate	−	2.19	4.25	9.67	5
l-Lysine	−	2.18	8.95	10.5	10
Sugars and related compounds
d-Glucose	−				5
d-Gluconate	−	3.76			<2
Esters
Acetic acid ethyl ester	ND				40
Formic acid methyl ester	ND				10
Succinic acid diethyl ester	ND				80
Lactic acid methyl ester	ND				60
d-3-Hydroxybutyric acid	ND				85
Methyl ester

^aThe uptake rates of [¹⁴C]succinate (3 mM) were determined in the absence or presence of 17 mM competitive unlabeled compound at pH 6.5. ND, not determined; +, good growth; ±, poor growth; −, no growth.