NOVEL PATHWAY FOR CONVERSION OF CHLOROHYDROXYQUINOL TO MALEYLACETATE IN BURKHOLDERIA-CEPACIA AC1100

Burkholderia cepacia AC 1100 metabolizes 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) via formation of 5-chlorohydroxyquinol (5-CHQ), hydroxy quinol (HQ), maleylacetate, and beta-oxoadipate. The step(s) leading t o the dechlorination of 5-CHQ to HQ has remained unidentified. We demo nstrate that a dechlorinating enzyme, TftG, catalyzes the conversion o f 5-CHQ to hydroxybenzoquinone, which is then reduced to HQ by a hydro xybenzoquinone reductase (HBQ reductase). HQ is subsequently converted to maleylacetate by hydroxyquinol 1,2-dioxygenase (HQDO). All three e nzymes were purified. We demonstrate specific product formation by col orimetric assay and mass spectrometry when 5-CHQ is treated successive ly with the three enzymes: TftG, TftG plus HBQ reductase, and TftG plu s HBQ reductase plus HQDO, This study delineates the complete enzymati c pathway for the degradation of 5-CHQ to maleylacetate.