Citation

Wojcieszyńska D, Greń I, Łabuzek S. Postepy Mikrobiologii 2005; 44(1): 63-70.

Copyright

(Copyright © 2005)

DOI

unavailable

PMID

unavailable

Abstract

Oxygen-activating enzymes with mononuclear non-heme active participate in many important metabolic pathways of the environmental significance. The ring dihydroxylation is non-specific preliminary step in the catabolic pathway and plays an important role in the activation of resonance-stabilized aromatic compounds before the subsequent catabolism. Dihydroxylate intermediates such as catechol, hydroxyquinol or protocatechuate are cleavaged between their two hydroxyl groups (ortho cleavage) by catechol 1,2-dioxygenase, hydroxyquinol 1,2-dioxygenase or protocatechuate 3,4-dioxygenase. The iron atom in the pentacoordinate active centre of these enzymes remains in the high-spin Fe (III) state during catalysis. Extradiol dioxygenases catalyze the ring-cleavage at the C-C bond adjacent to the vicinal hydroxyl groups. These dioxygenases typically contain non-heme iron Fe (II) in their active site but have been also shown to be active with Mn (II). The catechol 2,3-dioxygenase catalytic cycle is supposed to comprise a complexion of iron ion by monoanionic catecholate as a bidentate ligand. The ring cleavage reaction is proposed to proceed via an attack of the iron-bound activated oxygen on the nonhydroxylated position vicinal to the carbon atom bearing the phenolate anion. When extradiol dioxygenases cleave 3-chlorocatechol, they usually become inactivated. This inactivation might be caused by the strong chelating activity of 3-chlorocatechol or by suicide inactivation of the enzyme due to the formation of reactive intermediate.

Language: pl

Keywords

review; nonhuman; enzyme activity; protein degradation; chemical reaction; chemical structure; chelation; chemical bond; aromatic compound; catabolism; dihydroxylation; Intra- and extradiol dioxygenases; Meta-cleavage; oxygenase