Characterisation of a chromosomally encoded catechol 1,2-dioxygenase (E.C. 1.13.11.1) from Alcaligenes eutrophus CH34 |
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Authors: | G Sauret-Ignazi Jean Gagnon Claude Béguin Michel Barrelle Yves Markowicz Jean Pelmont Ariane Toussaint |
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Institution: | (1) Laboratoire de Génétique Microbienne (DRED JE 117), Université Joseph Fourier, BP 53, F-38041 Grenoble cédex 9, France Tel. +33-7651-4346; Fax +33-7651-4336 e-mail: jpelmont@bio.grenet.fr, FR;(2) Laboratoire d’Enzymologie Moléculaire, Institut de Biologie Structurale (CEA-CNRS UPR 9015), 41 avenue des Martyrs, F-38021 Grenoble cédex 1, France, FR;(3) Laboratoire d’Etudes Dynamiques et Structurales de la Sélectivité 2 (CNRS URA 332), Université Joseph Fourier, BP 53, F-38041 Grenoble cédex 9, France, FR |
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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 K
m for catechol is the lowest among known catechol and chlorocatechol dioxygenases. Similar K
m 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 K
m (or K
i) 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.
Received: 20 November 1996 / Accepted: 11 April 1996 |
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Keywords: | Catechol 1 2-dioxygenase Alcaligenes eutrophus CH34 Substituted catechol degradation Excess substrate inhibition Phenol interactions |
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