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Characterization of Hybrid Toluate and Benzoate Dioxygenases
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Zeitschriftentitel: | Journal of Bacteriology |
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Personen und Körperschaften: | , |
In: | Journal of Bacteriology, 185, 2003, 18, S. 5333-5341 |
Format: | E-Article |
Sprache: | Englisch |
veröffentlicht: |
American Society for Microbiology
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Schlagwörter: |
Zusammenfassung: | <jats:title>ABSTRACT</jats:title> <jats:p> Toluate dioxygenase of <jats:italic>Pseudomonas putida</jats:italic> mt-2 (TADO <jats:sub>mt2</jats:sub> ) and benzoate dioxygenase of <jats:italic>Acinetobacter calcoaceticus</jats:italic> ADP1 (BADO <jats:sub>ADP1</jats:sub> ) catalyze the 1,2-dihydroxylation of different ranges of benzoates. The catalytic component of these enzymes is an oxygenase consisting of two subunits. To investigate the structural determinants of substrate specificity in these ring-hydroxylating dioxygenases, hybrid oxygenases consisting of the α subunit of one enzyme and the β subunit of the other were prepared, and their respective specificities were compared to those of the parent enzymes. Reconstituted BADO <jats:sub>ADP1</jats:sub> utilized four of the seven tested benzoates in the following order of apparent specificity: benzoate > 3-methylbenzoate > 3-chlorobenzoate > 2-methylbenzoate. This is a significantly narrower apparent specificity than for TADO <jats:sub>mt2</jats:sub> (3-methylbenzoate > benzoate ∼ 3-chlorobenzoate > 4-methylbenzoate ∼ 4-chlorobenzoate ≫ 2-methylbenzoate ∼ 2-chlorobenzoate [Y. Ge, F. H. Vaillancourt, N. Y. Agar, and L. D. Eltis, J. Bacteriol. 184:4096-4103, 2002]). The apparent substrate specificity of the α <jats:sub>B</jats:sub> β <jats:sub>T</jats:sub> hybrid oxygenase for these benzoates corresponded to that of BADO <jats:sub>ADP1</jats:sub> , the parent from which the α subunit originated. In contrast, the apparent substrate specificity of the α <jats:sub>T</jats:sub> β <jats:sub>B</jats:sub> hybrid oxygenase differed slightly from that of TADO <jats:sub>mt2</jats:sub> (3-chlorobenzoate > 3-methylbenzoate > benzoate ∼ 4-methylbenzoate > 4-chlorobenzoate > 2-methylbenzoate > 2-chlorobenzoate). Moreover, the α <jats:sub>T</jats:sub> β <jats:sub>B</jats:sub> hybrid catalyzed the 1,6-dihydroxylation of 2-methylbenzoate, not the 1,2-dihydroxylation catalyzed by the TADO <jats:sub>mt2</jats:sub> parent. Finally, the turnover of this <jats:italic>ortho</jats:italic> -substituted benzoate was much better coupled to O <jats:sub>2</jats:sub> utilization in the hybrid than in the parent. Overall, these results support the notion that the α subunit harbors the principal determinants of specificity in ring-hydroxylating dioxygenases. However, they also demonstrate that the β subunit contributes significantly to the enzyme's function. </jats:p> |
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Umfang: | 5333-5341 |
ISSN: |
0021-9193
1098-5530 |
DOI: | 10.1128/jb.185.18.5333-5341.2003 |