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Applied and Environmental Microbiology, July 2003, p. 3924-3931, Vol. 69, No. 7
0099-2240/03/$08.00+0 DOI: 10.1128/AEM.69.7.3924-3931.2003
Regio- and Stereoselective Metabolism of 7,12-Dimethylbenz[a]anthracene by Mycobacterium vanbaalenii PYR-1
Joanna D. Moody,1 Peter P. Fu,2 James P. Freeman,3 and Carl E. Cerniglia1*
Division of Microbiology,1
Division of Biochemical Toxicology,2
Division of Chemistry, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, Arkansas 720793
Received 2 January 2003/
Accepted 7 April 2003
The degradation of 7,12-dimethylbenz[a]anthracene (DMBA), a carcinogenic polycyclic aromatic hydrocarbon, by cultures of Mycobacterium vanbaalenii PYR-1 was studied. When M. vanbaalenii PYR-1 was grown in the presence of DMBA for 136 h, high-pressure liquid chromatography (HPLC) analysis showed the presence of four ethyl acetate-extractable compounds and unutilized substrate. Characterization of the metabolites by mass and nuclear magnetic resonance spectrometry indicated initial attack at the C-5 and C-6 positions and on the methyl group attached to C-7 of DMBA. The metabolites were identified as cis-5,6-dihydro-5,6-dihydroxy-7,12-dimethylbenz[a]anthracene (DMBA cis-5,6-dihydrodiol), trans-5,6-dihydro-5,6-dihydroxy-7,12-dimethylbenz[a]anthracene (DMBA trans-5,6-dihydrodiol), and 7-hydroxymethyl-12-methylbenz[a]anthracene, suggesting dioxygenation and monooxygenation reactions. Chiral stationary-phase HPLC analysis of the dihydrodiols showed that DMBA cis-5,6-dihydrodiol had 95% 5S,6R and 5% 5R,6S absolute stereochemistry. On the other hand, the DMBA trans-5,6-dihydrodiol was a 100% 5S,6S enantiomer. A minor photooxidation product, 7,12-epidioxy-7,12-dimethylbenz[a]anthracene, was also formed. The results demonstrate that M. vanbaalenii PYR-1 is highly regio- and stereoselective in the degradation of DMBA.
* Corresponding author. Mailing address: National Center for Toxicological Research, HFT-250, Jefferson, AR 72079. Phone: (870) 543-7341. Fax: (870) 543-7307. E-mail: CCerniglia{at}nctr.fda.gov.
Applied and Environmental Microbiology, July 2003, p. 3924-3931, Vol. 69, No. 7
0099-2240/03/$08.00+0 DOI: 10.1128/AEM.69.7.3924-3931.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
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Copyright © 2003 by the American Society for Microbiology. All rights reserved.