HPLC profiles of the reaction products generated by cell extracts containing NbaA and/or NbaB. (A) Authentic standards 2-NBA, 2-HABA, 3-HAA, and NADPH. (B) Identification of 2-HABA as a reaction product produced by cell extracts containing NbaA. A total of 0.25 μmol of 2-NBA and 0.96 μmol of NADPH were incubated with NbaA in 30 mM potassium phosphate buffer (pH 7.0) at a total volume of 500 μl. The reaction mixture was analyzed by HPLC after 10 min of incubation at 30°C. (C) Identification of 3-HAA as a reaction product produced by cell extracts containing NbaA and NbaB. The reaction mixture, the same as that described above (B), was incubated for 10 min at 30°C, and aliquots of cell extracts containing NbaB were then added and further incubated for 10 min before the assay. In all cases, no product formation was generated in the absence of the added heterologous enzymes.