Table 1.

Enzymatic activities of wt and mutant cd₁ NIR

NIR	Nitrite reductase*		Oxygen reductase†
	Km, μM	Turnover number, s−1	Km, μM	Kcat, μM min−1
wt	6	8	2.0 (±0.5)	1.5 (±0.5)
H327A	—	0.08	1.8 (±0.8)	2.6 (±0.5)
H369A	—	0.08	7.5 (±2)	1.9 (±0.6)

^*pH 6.2 and 25°C. Error is ±20%. 

^† pH 7.0 and 20°C. K_m values were obtained with cytochrome c₅₅₁ as a substrate.