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J Bacteriol. 1998 Jun;180(11):2849-53.

Distal cleavage of 3-chlorocatechol by an extradiol dioxygenase to 3-chloro-2-hydroxymuconic semialdehyde.

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Institut für Mikrobiologie, Universität Stuttgart, 70569 Stuttgart, Germany.


A 2,3-dihydroxybiphenyl 1,2-dioxygenase from the naphthalenesulfonate-degrading bacterium Sphingomonas sp. strain BN6 oxidized 3-chlorocatechol to a yellow product with a strongly pH-dependent absorption maximum at 378 nm. A titration curve suggested (de)protonation of an ionizable group with a pKa of 4.4. The product was isolated, purified, and converted, by treatment with diazomethane, to a dimethyl derivative and, by incubation with ammonium chloride, to a picolinic acid derivative. Mass spectra and 1H and 13C nuclear magnetic resonance (NMR) data for these two derivatives prove a 3-chloro-2-hydroxymuconic semialdehyde structure for the metabolite, resulting from distal (1,6) cleavage of 3-chlorocatechol. 3-Methylcatechol and 2,3-dihydroxybiphenyl are oxidized by this enzyme, in contrast, via proximal (2,3) cleavage.

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