Diverse oxygenations catalyzed by carbazole 1,9a-dioxygenase from Pseudomonas sp strain CA10

Carbazole 1,9a-dioxygenase (CARDO) from Pseudomonas sp. strain CA10 is a mu lticomponent enzyme that catalyzes the angular dioxygenation of carbazole, dibenzofuran, and dibenzo-p-dioxin. It was revealed by gas chromatography-m ass spectrometry and H-1 and C-13 nuclear magnetic resonance analyses that xanthene and phenoxathiin were converted to 2,2',3-trihydroxydiphenylmethan e and 2,2',3-trihydroxydiphenyl sulfide, respectively. Thus, for xanthene a nd phenoxathiin, angular dioxygenation by CARDO occurred at the angular pos ition adjacent to the oxygen atom to yield hetero ring-cleaved compounds. I n addition to the angular dioxygenation, CARDO catalyzed the cis dihydroxyl ation of polycyclic aromatic hydrocarbons and biphenyl. Naphthalene and bip henyl were converted by CARDO to cis-1,2-dihydroxy-1,2-dihydronaphthalene a nd cis-2,3-dihydroxy-2,3-dihydrobiphenyl, respectively. On the other hand, CARDO also catalyzed the monooxygenation of sulfur heteroatoms in dibenzoth iophene and of the benzylic methylenic group in fluorene to yield dibenzoth iophene-5-oxide and 9-hydroxyfluorene, respectively. These results indicate that CARDO has a broad substrate range and can catalyze diverse oxygenatio n: angular dioxygenation, cis dihydroxylation, and monooxygenation. The div erse oxygenation catalyzed by CARDO for several aromatic compounds might re flect the differences in the binding of the substrates to the reaction cent er of CARDO.