Hydroxylation of biphenyl by the yeast Trichosporon mucoides
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O R I G I N A L PA P E R
Rabea Sietmann · Elke Hammer · Joanna Moody · Carl E. Cerniglia · Frieder Schauer
Hydroxylation of biphenyl by the yeast Trichosporon mucoides
Received: 10 May 2000 / Revised: 24 August 2000 / Accepted: 8 September 2000 / Published online: 18 October 2000 © Springer-Verlag 2000
Abstract Hydroxylation of biphenyl by the dibenzofuran-degrading yeast Trichosporon mucoides SBUG 801 was studied. Glucose-grown cells degraded 40% of the biphenyl added within the first 24 h of incubation. The first step in the biotransformation pathway was the monohydroxylation of the biaryl compound to produce 2-, 3-, and 4-hydroxybiphenyl. Further oxidation produced seven dihydroxylated intermediates; the second hydroxyl group was added either on the aromatic ring already hydroxylated or on the second ring. Of all metabolites, 2,5-dihydroxybiphenyl accumulated in the supernatant in the highest concentration. The initial hydroxylation favors the 4-position to produce 4-hydroxybiphenyl, which is subsequently hydroxylated to form 3,4-dihydroxybiphenyl. When biphenyl was replaced as a substrate by 4-hydroxybiphenyl, further hydroxylation of the intermediate 3,4-dihydroxybiphenyl resulted in 3,4,4′-trihydroxybiphenyl. Incubation of T. mucoides with biphenyl and 18O2 indicated a monooxygenase-catalyzed reaction in the oxidation of biphenyl. The hydroxylation was inhibited by 1-aminobenzotriazole and metyrapone, known cytochrome P450 inhibitors. These results are very similar to those observed in the biotransformation of biphenyl in mammals. Keywords Biphenyl · Hydroxylation · Trichosporon · Cytochrome P450
Introduction Biphenyl is an aromatic compound ubiquitous in the environment due to its commercial use as a fungistat in the R. Sietmann (✉) · E. Hammer · F. Schauer Institut für Mikrobiologie und Molekularbiologie, Ernst-Moritz-Arndt-Universität, F.-L.-Jahn-Strasse 15, 17489 Greifswald, Germany e-mail: [email protected], Tel.: +49-3834-864210, Fax: +49-3834-864202 J. Moody · C. E. Cerniglia National Center for Toxicological Research, Food and Drug Administration, Jefferson, AK 720792, USA
packing of citrus fruits and in food preservatives, organic synthesis, heat transfer fluids, and dye carriers, and as an intermediate in the synthesis of polychlorinated biphenyls. Exposure of humans to biphenyl and highly chlorinated biphenyls has been associated with eye and skin disorders and with toxic effects on the liver, kidneys, and central and peripheral nervous system that possibly lead to cancer, immune dysfunction, behavioral changes, and teratogenic abnormalities (Fisher et al. 1998; Cogliano 1998). Environmental exposure to biphenyl can also occur since it is an end-product in the reductive dechlorination of polychlorinated biphenyls by anaerobic microorganisms in contaminated lake and river sediments (Natarajan et al. 1999). The first report on the metabolism of biphenyl was by Klingenberg (1891), who described the oxidation of this compound in dogs to 4-hydroxybiphenyl. Since then, num
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