Zaborina O, Daubaras D L, Zago A, Xun L, Saido K, Klem T, Nikolic D, Chakrabarty A M
Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
J Bacteriol. 1998 Sep;180(17):4667-75. doi: 10.1128/JB.180.17.4667-4675.1998.
Burkholderia cepacia AC1100 metabolizes 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) via formation of 5-chlorohydroxyquinol (5-CHQ), hydroxyquinol (HQ), maleylacetate, and beta-oxoadipate. The step(s) leading to the dechlorination of 5-CHQ to HQ has remained unidentified. We demonstrate that a dechlorinating enzyme, TftG, catalyzes the conversion of 5-CHQ to hydroxybenzoquinone, which is then reduced to HQ by a hydroxybenzoquinone reductase (HBQ reductase). HQ is subsequently converted to maleylacetate by hydroxyquinol 1,2-dioxygenase (HQDO). All three enzymes were purified. We demonstrate specific product formation by colorimetric assay and mass spectrometry when 5-CHQ is treated successively with the three enzymes: TftG, TftG plus HBQ reductase, and TftG plus HBQ reductase plus HQDO. This study delineates the complete enzymatic pathway for the degradation of 5-CHQ to maleylacetate.
洋葱伯克霍尔德菌AC1100通过形成5-氯羟基喹啉(5-CHQ)、羟基喹啉(HQ)、马来酰乙酸和β-氧代己二酸来代谢2,4,5-三氯苯氧乙酸(2,4,5-T)。导致5-CHQ脱氯生成HQ的步骤仍未明确。我们证明,一种脱氯酶TftG催化5-CHQ转化为羟基苯醌,然后由羟基苯醌还原酶(HBQ还原酶)将其还原为HQ。随后,HQ由羟基喹啉1,2-双加氧酶(HQDO)转化为马来酰乙酸。所有这三种酶均已纯化。当5-CHQ先后用三种酶TftG、TftG加HBQ还原酶、TftG加HBQ还原酶加HQDO处理时,我们通过比色测定法和质谱法证明了特定产物的形成。本研究描绘了5-CHQ降解为马来酰乙酸的完整酶促途径。