Studies on bacterial nitroreductases. Enzymes involved in reduction of aromatic nitro compounds in Escherichia coli

Enzymes involved in reduction of methyl p-nitrobenzoate in Escherichia coli B/r were oxygen-insensitive and precipitated between 30 and 60% ammonium sulfate saturation from cell-free extracts of the strain. The reductases were resolved by DEAE-cellulose column chromatography into three enzymes, NADH-linked, NAD(P)H-linked and NADPH-linked ones. These enzymes were flavoprotein which could be inactivated by dialysis against 1 M potassium bromide and could be reactivated by FMN. The NADH-linked and NAD(P)H-linked reductases were sensitive to dicumarol and exhibited menadione reductase activities. Aromatic nitro compounds with electron-withdrawing p-substituents were easily reduced by the NAD(P)H-linked reductase.