Table 1. Kinetic parametersa of NADPH and NADH diaphorase reactions that were catalyzed by Xac-FNR, pea-FNR and Ec-FNR, and the dissociation constants for the different complexes with NADP+ b.

	NADPH				NADH
FNR	K m (µM)	k cat (s−1)	k cat/K m (µM−1s−1)	K d (µM)	K m (mM)	k cat (s−1)	k cat/K m (µM−1s−1)	NADPH/NADH specificity
Xac-FNR	10.8±0.5	121.9 ±− 1.8	11.3	9.7±0.4	3.3±1.4	3.2±1.3	0.001	1600
pea-FNR	15.3±4.3 c	374.3±18 c	24.5 c	10.9±3.1c	14.3±3.9 c	7.0±2.1 c	0.0005 c	49060 c
Ec-FNR	8.3±1.3 c	38.2±3.5 c	4.6 c	5.9±0.6 c	<0.05 d	Nd e	Nd e	Nd e

^aEach parameter value represents the average of three independent determinations. A description of the calculation methods that were employed is reported in the Materials and Methods. The original data are depicted in Figure S2.

^bPotassium ferricyanide reduction was assessed using the diaphorase assay of Zanetti [41] in 50 mM Tris-HCl (pH 8.0) using NADPH or NADH as the substrate.

^cValues of parameters for pea-FNR and Ec-FNR were obtained from a reference [49].

^dAn estimate of the limit of the determination based on the tested sensitivity of the method.

^eNot determined.