1. The influence of halogen substituents on the 1,2-dioxygenation of catechols was investigated. The results obtained with the two isoenzymes pyrocatechase I and pyrocatechase II from the haloarene-utilizing Pseudomonas sp. B 13 and the pyrocatechase from benzoate-induced cells of Alcaligenes eutrophus B.9 were compared. 2. Substituents on catechol were found to interfere with O2 binding by the two isoenzymes from Pseudomonas sp. B 13, whereas the Km value for catechol kept constant at different O2 concentrations. 3. Electron-attracting substituents decreased the Km values for catechols. 4. Results from binding studies with substituted catechols demonstrated narrow stereospecificities of pyrocatechase I from pseudomonas sp. B 13 and the pyrocatechase from alcaligenes eutrophus B.9. In contrast, a low steric hindrance by substituents in the binding of catechols with pyrocatechase II was observed. 5. Low pK′1 values of substituted catechols resulted in low Michaelis constants. 6. Electron-attracting substituents such as halogen decreased the reaction rates of catechol 1,2-dioxygenation. The correlation of the Vmax. values observed with pyrocatechase II from Pseudomonas sp. B 13 with the substituent constant sigma+ (Okamoto–Brown equation) was distinctly greater than with Hammett's sigma values. The corresponding logVmax. against sigma+ correlation for pyrocatechase I was considerably disturbed by steric influences of the substituents.
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July 1978
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Research Article|
July 15 1978
Chemical structure and biodegradability of halogenated aromatic compounds. Substituent effects on 1,2-dioxygenation of catechol
Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1978 London: The Biochemical Society
1978
Biochem J (1978) 174 (1): 85–94.
Citation
E Dorn, H J Knackmuss; Chemical structure and biodegradability of halogenated aromatic compounds. Substituent effects on 1,2-dioxygenation of catechol. Biochem J 15 July 1978; 174 (1): 85–94. doi: https://doi.org/10.1042/bj1740085
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