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Journal of Bacteriology, June 2001, p. 3548-3555, Vol. 183, No. 12
Departamento de Química, Universidad
Técnica Federico Santa María, Valparaíso,
Chile,1 and Division of Microbiology,
Gesellschaft für Biotechnologische Forschung, Braunschweig,
Germany2
Received 13 November 2000/Accepted 2 April 2001
The attack by the bph-encoded biphenyl dioxygenase of
Burkholderia sp. strain LB400 on a number of symmetrical
ortho-substituted biphenyls or quasi
ortho-substituted biphenyl analogues has been investigated.
2,2'-Difluoro-, 2,2'-dibromo-, 2,2'-dinitro-, and 2,2'-dihydroxybiphenyl were accepted as substrates. Dioxygenation of
all of these compounds showed a strong preference for the
semisubstituted pair of vicinal ortho and meta
carbons, leading to the formation of 2'-substituted
2,3-dihydroxybiphenyls by subsequent elimination of HX (X = F, Br,
NO2, or OH). All of these products were further metabolized
by 2,3-dihydroxybiphenyl 1,2-dioxygenases of Burkholderia sp. strain LB400 or of Rhodococcus globerulus P6.
Dibenzofuran and dibenzodioxin, which may be regarded as analogues of
doubly ortho-substituted biphenyls or diphenylethers,
respectively, were attacked at the "quasi ortho" carbon
(the angular position 4a) and its neighbor. This shows that an aromatic
ring-hydroxylating dioxygenase of class IIB is able to attack angular
carbons. The catechols formed, 2,3,2'-trihydroxybiphenyl and
2,3,2'-trihydroxydiphenylether, were further metabolized by
2,3-dihydroxybiphenyl 1,2-dioxygenase. While angular attack by the
biphenyl dioxygenase was the main route of dibenzodioxin oxidation,
lateral dioxygenation leading to dihydrodiols was the major reaction
with dibenzofuran. These results indicate that this enzyme is capable
of hydroxylating ortho or angular carbons carrying a
variety of substituents which exert electron-withdrawing inductive
effects. They also support the view that the conversions of phenols
into catechols by ring-hydroxylating dioxygenases, such as the
transformation of 2,2'-dihydroxybiphenyl into
2,3,2'-trihydroxybiphenyl, are the results of di- rather than of
monooxygenations. Lateral dioxygenation of dibenzofuran and subsequent
dehydrogenation and extradiol dioxygenation by a number of
biphenyl-degrading strains yielded intensely colored dead-end products.
Thus, dibenzofuran can be a useful chromogenic indicator for the
activity of the first three enzymes of biphenyl catabolic pathways.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.12.3548-3555.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Dehalogenation, Denitration, Dehydroxylation, and Angular
Attack on Substituted Biphenyls and Related Compounds by a
Biphenyl Dioxygenase
*
Corresponding author. Mailing address: Department of
Microbiology, Gesellschaft für Biotechnologische Forschung,
Mascheroder Weg 1, D-38124 Braunschweig, Germany. Phone: (49-531)
6181467. Fax: (49-531) 6181411. E-mail: bho{at}gbf.de.
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