METABOLISM OF POLYCHLORINATED PHENOLS BY PSEUDOMONAS-CEPACIA-AC1100 -DETERMINATION OF THE FIRST 2 STEPS AND SPECIFIC INHIBITORY EFFECT OF METHIMAZOLE

Resting cells of 2,4,5-trichlorophenoxyacetic acid-grown Pseudomonas c epacia AC1100 metabolize both dichlorophenols, such as 2,4 dichlorophe nol, 2,6-dichlorophenol, 3,4-dichlorophenol, and 3,5-dichlorophenol, a nd more highly substituted phenols, such as 2,4,6-trichlorophenol and pentachlorophenol, to the corresponding chlorohydroquinones. The first hydroxylation occurs in the para position of the phenol regardless of whether this position is replaced by a chlorine substituent. The firs t evidence leading to the characterization of para-hydroxylase as a fl avin-containing enzyme is provided by the inhibitory effect of methima zole, an alternate substrate for this monooxygenase; on the degradativ e ability of the strain, In a second step, with tetrachlorohydroquinon e, trichlorohydroxyquinone was isolated and completely characterized. Trichlorohydroxyquinone was also obtained from tetrachloroquinone. Inc ubation of the cells in the presence of an external source of NADPH pr events the further degradation of tetrachlorohydroquinone, suggesting that the,quinone derived from the two-electron oxidation of the hydroq uinone is more likely the substrate for the second hydroxylation.