Table 3.

Stability and Kinetic Parameters of PTE Variants

Variant	Muta	Normalized Activityb	Inactivation Temperature (°C)		T1/2 Chelatorc (min)	KM (mM)d	kcat × 105 (min-1) d	kcat/KM × 109 (min-1M-1) d
Lysate	Purified
PTE-S5	3	1	50.9 ± 0.7	52.4 ± 0.2	7.5 ± 0.3	0.101 ± 0.023	0.970 ± 0.076	0.96 ± 0.33
dPTE1	9	2.0	54.7 ± 3.2	NDe	NDe	NDe	NDe	NDe
dPTE2	19	6.1	59.2 ± 0.7	62.0 ± 0.2	51.2 ± 5.1	0.060 ± 0.014	0.70 ± 0.05	1.17 ± 0.35
dPTE3	28	2.3	47.0 ± 1.3	NDe	NDe	NDe	NDe	NDe

^aNumber of mutations relative to wild-type PTE.

^bFold increase in activity in crude E. coli lysates relative to PTE-S5.

^cChelator, 50 μM 1,10-phenanthroline.

^dKinetic parameters for paraoxon.

^eND, not determined.