Table 2. Relative percent activity of His-6-PnpA on deferent nitroaromatic compounds.

Substrate	Relative activity (%)
p-Nitrophenol	100 ± 3
o-Nitrophenol	15 ± 2
m-Nitrophenol	Nd
3-Methyl 4-nitrophenol	66 ± 3
4-Nitrocatechol	41 ± 2
2-Chloro 4-nitrophenol	25 ± 4
4-Chloro 2-nitrophenol	Nd
2,6-Dichlorophenol	18 ± 2
2,6-Dinitrophenol	15 ± 4
2-Amino 4-nitrophenol	38 ± 3
Pentachlorophenol	12 ± 4
Catechol	Nd
4-Chlorocatechol	Nd

The relative percent activity was measured by HPLC analysis, and standard deviation values were calculated using taking the mean of triplicate experiments.

Nd= activity not observed.