Mechanism of extradiol catechol dioxygenases: evidence for a lactone intermediate in the 2,3-dihydroxyphenylpropionate 1,2-dioxygenase reaction

Sanvoisin, Jonathan, Langley, G. John and Bugg, Timothy D.H. (1995) Mechanism of extradiol catechol dioxygenases: evidence for a lactone intermediate in the 2,3-dihydroxyphenylpropionate 1,2-dioxygenase reaction. Journal of the American Chemical Society, 117 (29), 7836-7837. (doi:10.1021/ja00134a041).

Abstract

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The oxidative cleavage of catechols by non-heme iron-dependent dioxygenase enzymes is a key step in the bacterial degradation of naturally-occurring and man-made aromatic compounds.1 Two classes of catechol dioxygenases are found: iron(UI)-dependent intradiol dioxygenases, which cleave the carbon—carbon bond between the two hydroxyl groups, and iron(II)-dependent extradiol dioxygenases, which cleave a carbon—carbon bond adjacent to the two hydroxyl groups. Despite extensive spectroscopic studies on these enzymes and the determination of the crystal structure of protocatechuate 3,4-dioxygenase,3 45only limited data are available regarding the mechanism of carbon—carbon bond cleavage. A dioxetane intermediate was originally proposed for the .intradiol enzyme catechol 1,2-dioxygenase based on 1S02 labeling studies; however, more recently an anhydride intermediate has been proposed for the intradiol class, formed by a Criegee rearrangement. In view of the key environmental significance of the catechol dioxygenases and the absence of mechanistic information regarding the extradiol enzymes, we have initiated a study of the mechanism of iron(II)-dependent 2,3-dihydroxyphenyl-propionate 1,2-dioxygenase (MhpB) from Escherichia coli. Here we report evidence from 18G labeling studies and analogue synthesis for a lactone intermediate.

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Contributors

Author: G. John Langley

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