Detailed comparison between the substrate specificities of two angular dioxygenases, dibenzofuran 4,4a-dioxygenase from Terrabacter sp. and carbazole 1,9a-dioxygenase from Pseudomonas resinovorans

The preferred substrates in angular dioxygenation, monooxygenation, and lateral dioxygenation by dibenzofuran 4,4a-dioxygenase (DFDO) from Terrabacter sp. strain DBF63 and carbazole 1,9a-dioxygenase (CARDO) from Pseudomonas resinovorans strain CA10 are shown to be distinctly different. The preferred oxygenation reactions suggest that DFDO evolved from a polycyclic aromatic hydrocarbon dioxygenase and that its most preferred substrates were fluorene and 9-fluorenone. The angular dioxygenases involved in the degradation pathway of dibenzofuran (dioxin) and fluorene are closely related in function, while CARDO is a novel enzyme not only phylogenetically but also functionally.