Table II.

Steady-state kinetic constants for MoR fragments

NR Fragment	Km			Vmax		kcat		kcat/Km
	μm			μmol min−1 mol−1 heme		s−1 for 1 e−		μm−1 s−1
	NADH	FeCN	Cyt c	FeCN	Cyt c	FeCN	Cyt c	NADH-Fa	NADH-C	FeCN	Cyt c
SoMoR	13	32	6	80	55	2,700	1,800	200	140	80	300
ZmMoR	10	17	6	69	40	2,300	1,300	230	130	140	220
ZmMoR+	10	17	6	69	40	2,300	1,300	230	130	140	220

Kinetics were analyzed on the HP 8453 spectrophotometer as described in “Materials and Methods” at 25°C, in 30 mm MOPS, pH 7.0. NADH, FeCN, and Cyt c were varied from 5 to 90 μm, 5 to 200 μm, and 5 to 50 μm, respectively. True K_m and V_max were determined from replots of the apparent kinetic constants at each concentration of the “fixed” or second substrate (Campbell and Smarrelli, 1978), after the apparent kinetic constants were determined with the EnzPack program (Biosoft, Ferguson, MO) using the observed initial velocities at each substrate concentration for every concentration of the second substrate.

^ak_cat/K_m for NADH in the reaction with FeCN is designated NADH-F and for Cyt c reduction, NADH-C.