Authors: Vaillancourt, Frédéric¹; Bolin, Jeffrey²; Eltis, Lindsay³

Source: Critical Reviews in Biochemistry and Molecular Biology, Volume 41, Number 4, July-August 2006 , pp. 241-267(27)

Publisher: Informa Healthcare

Abstract:

Ring-cleaving dioxygenases catalyze the oxygenolytic fission of catecholic compounds, a critical step in the aerobic degradation of aromatic compounds by bacteria. Two classes of these enzymes have been identified, based on the mode of ring cleavage: intradiol dioxygenases utilize non-heme Fe(III) to cleave the aromatic nucleus ortho to the hydroxyl substituents; and extradiol dioxygenases utilize non-heme Fe(II) or other divalent metal ions to cleave the aromatic nucleus meta to the hydroxyl substituents. Recent genomic, structural, spectroscopic, and kinetic studies have increased our understanding of the distribution, evolution, and mechanisms of these enzymes. Overall, extradiol dioxygenases appear to be more versatile than their intradiol counterparts. Thus, the former cleave a wider variety of substrates, have evolved on a larger number of structural scaffolds, and occur in a wider variety of pathways, including biosynthetic pathways and pathways that degrade non-aromatic compounds. The catalytic mechanisms of the two enzymes proceed via similar iron-alkylperoxo intermediates. The ability of extradiol enzymes to act on a variety of non-catecholic compounds is consistent with proposed differences in the breakdown of this iron-alkylperoxo intermediate in the two enzymes, involving alkenyl migration in extradiol enzymes and acyl migration in intradiol enzymes. Nevertheless, despite recent advances in our understanding of these fascinating enzymes, the major determinant of the mode of ring cleavage remains unknown.

Keywords: extradiol dioxygenase; intradiol dioxygenase; catechol; protocatechuate; gentisate; salicylate; hydroxyquinol; hydroquinone; aminophenol; vicinal oxygen chelate superfamily; cupin superfamily

Document Type: Research article

DOI: http://dx.doi.org/10.1080/10409230600817422

Affiliations: 1: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA 2: Purdue Cancer Center and Markey Center for Structural Biology, Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA 3: Departments of Microbiology and Biochemistry, University of British Columbia, Vancouver, Canada

Publication date: 2006-07-01

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