Use of 4-nitrophenoxyacetic acid for detection and quantification of 2,4-dichlorophenoxyacetic acid (2,4-D)/α-ketoglutarate dioxygenase activity in 2,4-D-degrading microorganisms

Abstract

Purified 2,4-dichlorophenoxyacetic acid (2,4-D)/α-ketoglutarate dioxygenase (TfdA) was shown to use 4-nitrophenoxyacetic acid (K(m) = 0.89 ± 0.04 mM, k(cat) [catalytic constant] = 540 ± 10 min-1), producing intensely yellow 4-nitrophenol. This reagent was used to develop a rapid, continuous, colorimetric assay for the detection of TfdA and analogous activities in 2,4-D-degrading bacterial cells and extracts.