Table 1.

Parameters obtained from kinetic and equilibrium measurements on PNPOx forms

Names of parameters listed in the table refer to Scheme 1A.

Parameter	WT	Apo-WT	Quadruple mutant
Kinetics of PNP oxidation
kcat (s−1)a	0.3 (15)		5.3 × 10−4 ± 0.7 × 10−4
KD (μm)a	2 (15)		238 ± 77
kcat (s−1)b	0.28 ± 0.01
KD (μm)b	1.6 ± 0.4
Inhibition kinetics
kcat (s−1)c	0.27 ± 0.01
KD (μm)c	0.90 ± 0.55
KDp (μm)c	12.85 ± 1.68
KI (μm)c	0.59 ± 0.7
KIs (μm)c	7.13 ± 0.52
PLP binding
kon (μm−1 s−1)d	11.35 ± 1.27
koff (s−1)d	3.24 ± 2.24
KI (μm)d	0.28 ± 0.19
KI (μm)e	0.15 ± 0.04	0.28 ± 0.01	0.45 ± 0.02

^a Determined in Tris buffer.

^b Determined in HEPES buffer from fitting of initial velocity.

^c Determined from PLP inhibition kinetics.

^d Determined from rapid kinetics measurements of PLP binding.

^e Determined from equilibrium measurements.