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Regiospecificity of two multicomponent monooxygenases from Pseudomonas stutzeri OX1: molecular basis for catabolic adaptation of this microorganism to methylated aromatic compounds
- Source :
- Applied and environmental microbiology. 71(8)
- Publication Year :
- 2005
-
Abstract
- The pathways for degradation of aromatic hydrocarbons are constantly modified by a variety of genetic mechanisms. Genetic studies carried out with Pseudomonas stutzeri OX1 suggested that the tou operon coding for toluene o -xylene monooxygenase (ToMO) was recently recruited into a preexisting pathway that already possessed the ph operon coding for phenol hydroxylase (PH). This apparently resulted in a redundancy of enzymatic activities, because both enzymes are able to hydroxylate (methyl)benzenes to (methyl)catechols via the intermediate production of (methyl)phenols. We investigated the kinetics and regioselectivity of toluene and o -xylene oxidation using Escherichia coli cells expressing ToMO and PH complexes. Our data indicate that in the recombinant system the enzymes act sequentially and that their catalytic efficiency and regioselectivity optimize the degradation of toluene and o -xylene, both of which are growth substrates. The main product of toluene oxidation by ToMO is p -cresol, the best substrate for PH, which catalyzes its transformation to 4-methylcatechol. The sequential action of the two enzymes on o -xylene leads, via the intermediate 3,4-dimethylphenol, to the exclusive production of 3,4-dimethylcatechol, the only dimethylcatechol isomer that can serve as a carbon and energy source after further metabolic processing. Moreover, our data strongly support a metabolic explanation for the acquisition of the ToMO operon by P. stutzeri OX1. It is possible that using the two enzymes in a concerted fashion confers on the strain a selective advantage based on the ability of the microorganism to optimize the efficiency of the use of nonhydroxylated aromatic hydrocarbons, such as benzene, toluene, and o -xylene.
- Subjects :
- phenol hydroxylase
Operon
Stereochemistry
toluene o-xylene monooxygenase
Xylenes
Applied Microbiology and Biotechnology
Hydrocarbons, Aromatic
Mixed Function Oxygenases
Substrate Specificity
chemistry.chemical_compound
Multienzyme Complexes
Pseudomonas
Escherichia coli
Enzymology and Protein Engineering
Pseudomonas stutzeri
Ecology
biology
Regioselectivity
Gene Expression Regulation, Bacterial
Monooxygenase
biology.organism_classification
Toluene
Adaptation, Physiological
Toluene oxidation
Kinetics
Biodegradation, Environmental
chemistry
Oxygenases
Energy source
Oxidation-Reduction
Food Science
Biotechnology
Subjects
Details
- ISSN :
- 00992240
- Volume :
- 71
- Issue :
- 8
- Database :
- OpenAIRE
- Journal :
- Applied and environmental microbiology
- Accession number :
- edsair.doi.dedup.....4f1624f91ebad04ea9e4b18d46999465