Fig. 2.

Nitrite produced by E. coli cultures expressing the 2NTDO variants in 6 h whole-cell reactions with nitrobenzene (white), 2NT (light grey), 3NT (dark grey), or 4NT (black) as substrates. The wild-type and evolved dioxygenases are labeled with the names of the parental strains; the other enzymes were generated by site-directed mutagenesis. The S242N and L238V S242N mutants did not produce detectable amounts of nitrite from any of the substrates. Fold increases in activity with 4NT are indicated. Error bars indicate standard deviations (N = 3).