title: Distal cleavage of 3-chlorocatechol by an extradiol dioxygenase to 3-chloro-2-hydroxymuconic semialdehyde.
abstract: 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.
authors.affiliation: Institut für Mikrobiologie, Universität Stuttgart, 70569 Stuttgart, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Riegert
authors.forename: G
authors.initials: G
authors.lastname: Heiss
authors.forename: P
authors.initials: P
authors.lastname: Fischer
authors.forename: A
authors.initials: A
authors.lastname: Stolz
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D000643:Ammonium Chloride; D002396:Catechols / Q000737:chemistry*; D003978:Diazomethane; D049308:Dioxygenases; D004926:Escherichia coli / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D006867:Hydrolases / Q000378:metabolism; D013058:Mass Spectrometry; D008956:Models, Chemical; D019906:Nuclear Magnetic Resonance, Biomolecular; D010105:Oxygenases / Q000378:metabolism*; D010848:Picolinic Acids / Q000737:chemistry; D011506:Proteins; D013011:Sorbic Acid / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C112601:3-chloro-2-hydroxymuconic semialdehyde; D000447:Aldehydes; D002396:Catechols; D010848:Picolinic Acids; D011506:Proteins; D000643:Ammonium Chloride; C031136:3-methylcatechol; C031137:3-chlorocatechol; D003978:Diazomethane; D010105:Oxygenases; D049308:Dioxygenases; C074272:2,3-dihydroxybiphenyl oxygenase; D006867:Hydrolases; C092541:2-hydroxymuconate-semialdehyde hydrolase; D013011:Sorbic Acid