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Modulation of FAD-dependent monooxygenase activity from aromatic compounds-degrading Stenotrophomonas maltophilia strain KB2

100%
Wojcieszyńska D., Greń I., Hupert-Kocurek K., Guzik U.
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2011
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vol. 58
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issue 3
421-426
EN
The purpose of this study was purification and characterization of phenol monooxygenase from Stenotrophomonas maltophilia strain KB2, enzyme that catabolises phenol and its derivatives through the initial hydroxylation to catechols. The enzyme requires NADH and FAD as a cofactors for activity, catalyses hydroxylation of a wide range of monocyclic phenols, aromatic acids and dihydroxylated derivatives of benzene except for catechol. High activity of this monooxygenase was observed in cell extract of strain KB2 grown on phenol, 2-methylphenol, 3-metylphenol or 4-methylphenol. Ionic surfactants as well as cytochrome P450 inhibitors or 1,4-dioxane, acetone and n-butyl acetate inhibited the enzyme activity, while non-ionic surfactants, chloroethane, ethylbenzene, ethyl acetate, cyclohexane, and benzene enhanced it. These results indicate that the phenol monooxygenase from Stenotrophomonas maltophilia strain KB2 holds great potential for bioremediation.
2
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Altering substrate specificity of catechol 2,3-dioxygenase from Planococcus sp. strain S5 by random mutagenesis

100%
Hupert-Kocurek K., Wojcieszyńska D., Guzik U.
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2014
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vol. 61
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issue 4
705-710
EN
c23o gene, encoding catechol 2,3-dioxygenase from Planococcus sp. strain S5 was randomly mutagenized to generate variant forms of the enzyme with higher degradation activity. Additionally, the effect of introduced mutations on the enzyme structure was analyzed based on the putative 3D models the wild-type and mutant enzymes. C23OB58 and C23OB81 mutant proteins with amino acid substitutions in close proximity to the enzyme surface or at the interface and in the vicinity of the enzyme active site respectively showed the lowest activity towards all catecholic substrates. The relative activity of C23OC61 mutant towards para-substituted catechols was 20-30% lower of the wild-type enzyme. In this mutant all changes: F191I, C268R, Y272H, V280A and Y293D were located within the conserved regions of C-terminal domain. From these F191I seems to have significant implications for enzyme activity. The highest activity towards different catechols was found for mutant C23OB65. R296Q mutation improved the activity of C23O especially against 4-chlorocatechol. The relative activity of above-mentioned mutant detected against this substrate was almost 6-fold higher than the wild-type enzyme. These results should facilitate future engineering of the enzyme for bioremediation.
3
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Characterization of catechol 2,3-dioxygenase from Planococcus sp. strain S5 induced by high phenol concentration

100%
Hupert-Kocurek K., Guzik U., Wojcieszyńska D.
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2012
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vol. 59
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issue 3
345-351
EN
This study aimed at characterization of a new catechol 2,3-dioxygenase isolated from a Gram-positive bacterium able to utilize phenol as the sole carbon and energy source. Planococcus sp. strain S5 grown on 1 or 2 mM phenol showed activity of both a catechol 1,2- and catechol 2,3-dioxygenase while at a higher concentrations of phenol only catechol 2,3-dioxygenase activity was observed. The enzyme was optimally active at 60°C and pH 8.0. Kinetic studies showed that the Km and Vmax of the enzyme were 42.70 µM and 329.96 mU, respectively. The catechol 2,3-dioxygenase showed the following relative meta-cleavage activities for various catechols tested: catechol (100%), 3-methylcatechol (13.67%), 4-methylcatechol (106.33%) and 4-chlorocatechol (203.80%). The high reactivity of this enzyme towards 4-chlorocatechol is different from that observed for other catechol 2,3-dioxygenases. Nucleotide sequencing and homology search revealed that the gene encoding the S5 catechol 2,3-dioxygenase shared the greatest homology with the known genes encoding isoenzymes from Gram-negative Pseudomonas strains.
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