Table 1.

Spectrophotometric enzyme activity assays

Assay	Activitya		Fold purification
	Original sampleb	Partially purifiedc protein
Hydroxylamine oxidased	0.02 ± 0.006	0.16 ± 0.1	7.2
Hydrazine oxidased	0.09 ± 0.04	0.46 ± 0.1	5.1
Nitrite reductasee	0.052 ± 0.025	0.31 ± 0.1	6.0

^aFor all assays, activities are shown as units ± standard deviation (n = 3).

^bProtein concentration, 2.15 mg ml⁻¹.

^cProtein concentration, 0.15 mg ml⁻¹.

^dOne unit is defined as (1 μmol MTT/min)/(mg protein).

^eOne unit is defined as (1 μmol methyl viologen/min)/(mg protein).