Table 1. Kinetic Values of WT and Mutant ccNiR^a.

	KM (μM)	kcat (e– s–1)	kcat (% of WT)	KI (mM)	mol of MV/mol of NH4+
WT	100 ± 15	150 ± 20	100	11	5.0 ± 1.0
H257Q	NDc	NDc	0.8b	NDc	6.4 ± 0.6
Y206F	35 ± 15	9 ± 3	6.0	NAd	5.5 ± 0.1
R103Q	910 ± 130	82 ± 9	55	NAd	6.3 ± 0.5
R103K	340 ± 50	20 ± 5	13	NAd	6.0 ± 0.6

^aAll kinetic parameters were determined by PFV as described in Materials and Methods with the exception of H257Q.

^bBecause of low activity, the H257Q percent activity was measured in solution at 1 mM nitrite, pH 7, and 20 °C and compared to that of WT ccNiR, also measured in solution, under the same conditions. PFV was conducted at pH 7 and 20 mV/s with a rotation rate of 3000 rpm.

^cNot determined.

^dNot available.