title: Characterisation of a chromosomally encoded catechol 1,2-dioxygenase (E.C. 1.13.11.1) from Alcaligenes eutrophus CH34.
abstract: Alcaligenes eutrophus CH34 used benzoate as a sole source of carbon and energy, degrading it through the 3-oxoadipate pathway. All the enzymes required for this degradation were shown to be encoded by chromosomal genes. Catechol 1,2-dioxygenase activity was induced by benzoate, catechol, 4-chlorocatechol, and muconate. The enzyme is most likely a homodimer, with an apparent molecular weight of 76,000 +/- 500. According to several criteria, its properties are intermediate between those of catechol 1,2-dioxygenases (CatA) and chlorocatechol 1,2-dioxygenases (ClcA). The determined Km for catechol is the lowest among known catechol and chlorocatechol dioxygenases. Similar Km values were found for para-substituted catechols, although the catalytic constants were much lower. The catechol 1,2-dioxygenase from strain CH34 is unique in its property to transform tetrachlorocatechol; however, excess substrate led to a marked reversible inhibition. Some meta- and multi-substituted catechols behaved similarly. The determined Km (or Ki) values for para- or meta-substituted catechols suggest that the presence of an electron-withdrawing substituent at one of these positions results in a higher affinity of the enzyme for the ligand. Results of studies of recognition by the enzyme of various nonmetabolised aromatic compounds are also discussed.
authors.affiliation: Laboratoire de Génétique Microbienne (DRED JE 117), Université Joseph Fourier, BP 53, F-38041 Grenoble cédex 9, France.
authors.forename: G
authors.initials: G
authors.lastname: Sauret-Ignazi
authors.forename: J
authors.initials: J
authors.lastname: Gagnon
authors.forename: C
authors.initials: C
authors.lastname: Béguin
authors.forename: M
authors.initials: M
authors.lastname: Barrelle
authors.forename: Y
authors.initials: Y
authors.lastname: Markowicz
authors.forename: J
authors.initials: J
authors.lastname: Pelmont
authors.forename: A
authors.initials: A
authors.lastname: Toussaint
mesh_terms: D000421:Alcaligenes / Q000201:enzymology*; D000595:Amino Acid Sequence; D001565:Benzoates / Q000378:metabolism; D019817:Benzoic Acid; D050548:Catechol 1,2-Dioxygenase; D049308:Dioxygenases; D008969:Molecular Sequence Data; D010105:Oxygenases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D001565:Benzoates; D019817:Benzoic Acid; D010105:Oxygenases; D049308:Dioxygenases; D050548:Catechol 1,2-Dioxygenase