TABLE 3.

Activity of the purified lawsone reductase with different substrates and comparison of the results with values described earlier for NfsB^e

Substrated	λ (nm)	ɛ (mM−1 cm−1)f	Activity (U mg of protein−1) of:
			Lawsone reductasea	Nitroreductase Bb
Flavin mononucleotide	450	13	0.26	1
Flavin adenine dinucleotide	450	9.2	0.32	1
Riboflavin	450	10.7	0.27	2
1,4-Benzoquinonec	340	6.72g	41.7	251
Menaquinone	358	6.7g	16.7	60
Nitrofurazone	400	13	20.6	13
Nitrofurantoin	400	14.2	25.3	21
4-Nitrobenzoate	358	4.7g	0.10	1
4-Nitrotoluene	358	4.7g	0.04	0.4
4-Nitrophenol	400	14	0.75	0.1
4-Nitroaniline	400	14	0.02	0.1
K3[Fe(CN)6]	420	1	360	387
2,6-Dichloroindophenol	605	20	0.36	2
Methylenebluec	605	30	0	2

^aExperimental details are given in Materials and Methods.

^bNitroreductase B activities given by Zenno et al. (49). The authors determined the activity under aerobic conditions in a spectrophotometrical cuvette test at 23°C in Tris-HCl buffer (pH 7) using a 100 μM concentration of each of the respective substrates.

^c1,4-Benzoquinone and methyleneblue were reduced under the anaerobic test conditions spontaneously by NADH. The activities indicated were corrected for these spontaneous reactions.

^dThe activities for 1,4-benzoquinone, menaquinone, and the nitrocompounds were measured with 5% methanol in the test system to ensure proper dissolution of the substrates.

^eThe experiment was performed twice and the mean values are given.

^fThe reaction rates were determined at the indicated wavelength.

^gDecrease of NADH was measured at the indicated wavelengths.