TABLE 4.

Phosphate release from PA and 2PP in cell-free extracts and resting cells of E. coli DH5α with different plasmids, preinduced with PA

Plasmida	phnB gene	Phosphate release ± SD in
		Cell-free extractsb (nmol min−1 mg−1) with		Resting cellsc with
		PA	2PP	PA	2PP
PCA455	+	128.6 ± 1.6	1.03 ± 0.01	2.30 ± 0.03	0.45 ± 0.04
PCA452	−	85.5 ± 1.2	0.90 ± 0.1	2.40 ± 0.1	0.05 ± 0.02

^aIdentities of the inserts containing the phnA gene region are shown in Fig. 1. 

^bSpecific activity of PA hydrolase given as P_i release in nanomoles per minute per milligram. For this analysis, cultures of E. coli were grown and prepared as described in Materials and Methods. Cell-free extracts were then prepared and PA-hydrolase activity was assayed. 

^cActivity of PA hydrolase in resting cell cultures (OD₆₀₀ = 0.5) was assayed by P_i release (millimoles) after 16 h of incubation with the corresponding substrate (PA or 2PP) at 30°C. The results are expressed as an average of three experiments.