TABLE 2.

Comparison of the 3-hydroxybenzoate 6-hydroxylase specific activities from P25X wild-type with the xlnD mutant G50 when grown in lactate and in the presence of aromatic substrates

Carbon source for growth	Mean sp acta of P. alcaligenes cells ± SD assayed with:
	P25X		G50
	3-Hydroxybenzoate	3-Hydroxy- 4-methylbenzoate	3-Hydroxybenzoate	3-Hydroxy- 4-methylbenzoate
Lactateb	0.06 ± 0.01	0.09 ± 0.01	NDd	ND
3-Hydroxybenzoatec	0.16 ± 0.03	0.14 ± 0.02	0.14 ± 0.02	0.02 ± 0.01
3-Hydroxy-4-methylbenzoatec	0.14 ± 0.02	0.45 ± 0.03	ND	ND
Gentisatec	0.11 ± 0.02	0.26 ± 0.03	0.03 ± 0.01	<0.01

^aOne unit of enzyme activity is defined as the conversion of 1 μmol of NADH to NAD⁺ per min at 23°C. Specific activities are expressed as units per mg of protein. Values presented are the means of three separate experiments.

^bLactate, at a final concentration of 20 mM, was the sole carbon source in the basal minimal medium.

^cAromatic substrates were added (to a final concentration of 2.5 mM) into the cell culture grown in 20 mM lactate when the OD₆₀₀ was 0.5 to 0.6.

^dND, nondetectable activity.