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Applied and Environmental Microbiology, April 2004, p. 2211-2219, Vol. 70, No. 4
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.4.2211-2219.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Phenol Hydroxylase and Toluene/o-Xylene Monooxygenase from Pseudomonas stutzeri OX1: Interplay between Two Enzymes

Valeria Cafaro,1,{dagger} Viviana Izzo,1,{dagger} Roberta Scognamiglio,1,{dagger} Eugenio Notomista,1 Paola Capasso,1 Annarita Casbarra,2 Piero Pucci,2 and Alberto Di Donato1*

Dipartimento di Chimica Biologica, Università di Napoli Federico II, 16-80134 Naples,1 Dipartimento di Chimica Organica e Biochimica, Università di Napoli Federico II, 45-80126 Naples, Italy2

Received 26 August 2003/ Accepted 9 January 2004

Degradation of aromatic hydrocarbons by aerobic bacteria is generally divided into an upper pathway, which produces dihydroxylated aromatic intermediates by the action of monooxygenases, and a lower pathway, which processes these intermediates down to molecules that enter the citric acid cycle. Bacterial multicomponent monooxygenases (BMMs) are a family of enzymes divided into six distinct groups. Most bacterial genomes code for only one BMM, but a few cases (3 out of 31) of genomes coding for more than a single monooxygenase have been found. One such case is the genome of Pseudomonas stutzeri OX1, in which two different monooxygenases have been found, phenol hydroxylase (PH) and toluene/o-xylene monooxygenase (ToMO). We have already demonstrated that ToMO is an oligomeric protein whose subunits transfer electrons from NADH to oxygen, which is eventually incorporated into the aromatic substrate. However, no molecular data are available on the structure and on the mechanism of action of PH. To understand the metabolic significance of the association of two similar enzymatic activities in the same microorganism, we expressed and characterized this novel phenol hydroxylase. Our data indicate that the PH P component of PH transfers electrons from NADH to a subcomplex endowed with hydroxylase activity. Moreover, a regulatory function can be suggested for subunit PH M. Data on the specificity and the kinetic constants of ToMO and PH strongly support the hypothesis that coupling between the two enzymatic systems optimizes the use of nonhydroxylated aromatic molecules by the draining effect of PH on the product(s) of oxidation catalyzed by ToMO, thus avoiding phenol accumulation.

* Corresponding author. Mailing address: Dipartimento di Chimica Biologica, Università di Napoli Federico II, Via Mezzocannone, 16-80134 Naples, Italy. Phone: 39 81 674171. Fax: 39 81 676710. E-mail: didonato{at}unina.it.

{dagger} Valeria Cafaro, Viviana Izzo, and Roberta Scognamiglio contributed equally to this work.

Applied and Environmental Microbiology, April 2004, p. 2211-2219, Vol. 70, No. 4
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.4.2211-2219.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Notomista, E., Cafaro, V., Bozza, G., Di Donato, A. (2009). Molecular Determinants of the Regioselectivity of Toluene/o-Xylene Monooxygenase from Pseudomonas sp. Strain OX1. Appl. Environ. Microbiol. 75: 823-836 [Abstract] [Full Text]  
  • Kane, S. R., Chakicherla, A. Y., Chain, P. S. G., Schmidt, R., Shin, M. W., Legler, T. C., Scow, K. M., Larimer, F. W., Lucas, S. M., Richardson, P. M., Hristova, K. R. (2007). Whole-Genome Analysis of the Methyl tert-Butyl Ether-Degrading Beta-Proteobacterium Methylibium petroleiphilum PM1. J. Bacteriol. 189: 1931-1945 [Abstract] [Full Text]  
  • Lalucat, J., Bennasar, A., Bosch, R., Garcia-Valdes, E., Palleroni, N. J. (2006). Biology of Pseudomonas stutzeri. Microbiol. Mol. Biol. Rev. 70: 510-547 [Abstract] [Full Text]  
  • Cafaro, V., Notomista, E., Capasso, P., Di Donato, A. (2005). Regiospecificity of Two Multicomponent Monooxygenases from Pseudomonas stutzeri OX1: Molecular Basis for Catabolic Adaptation of This Microorganism to Methylated Aromatic Compounds. Appl. Environ. Microbiol. 71: 4736-4743 [Abstract] [Full Text]  


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