TABLE 1.

Kinetic parameters for PheH variants

Variant	Kdimera	Kactb	K0.5c	kcatc
	mm	mm	mm	min−1
Wild type	0.016 ± 0.001	0.054 ± 0.03d (2.4 ± 0.3)e	0.30 ± 0.01 (2.0 ± 0.1)	580 ± 10
A47G	0.23 ± 0.04	0.17 ± 0.01 (2.2 ± 0.5)	0.63 ± 0.04 (1.9 ± 0.2)	350 ± 10
E44Q	0.060 ± 0.010	NDf	ND	ND
L62V	0.063 ± 0.017	ND	ND	ND
H64N	1.7 ± 0.1	0.79 ± 0.08 (2.0 ± 0.3)	4.1 ± 0.4 (2.2 ± 0.4)	390 ± 30
L48V	4.1 ± 0.5	1.6 ± 0.1 (2.5 ± 0.2)	1.8 ± 0.4 (1.4 ± 0.2)	130 ± 20

^a K_d value for phenylalanine binding to RDPheH_25–117 determined by AUC.

^b K_d value for phenylalanine binding to PheH based on the fluorescence change in the presence of phenylalanine. The values are averages of at least three individual measurements.

^c Steady-state kinetic parameters with phenylalanine as substrate, after activation by 5–10 mm phenylalanine.

^d Data are from Ref. 25.

^e This is the Hill coefficient.

^f ND means not determined.