Part of the multicomponent carbazole 1,9a-dioxygenase (CARDO), that converts carbazole (CAR) into 2-aminobiphenyl-2,3-diol. Catalyzes the dioxygenation at the angular (C-9a) and adjacent (C-1) positions of carbazole to yield a highly unstable cis-hydrodiol intermediate which is spontaneously converted to 2-aminobiphenyl-2,3-diol. It is also able to attack the angular position adjacent of hetero atom of heterocyclic aromatic compounds such as polychlorinated dibenzo-p-dioxin (DD) and dibenzofuran (DBF). It was also shown that CARDO has the ability to metabolize biphenyl and polycyclic aromatic hydrocarbons, such as naphthalene and phenanthrene. 9H-carbazole + H(+) + NADH + O2 = 2'-aminobiphenyl-2,3-diol + NAD(+) 9H-carbazole + H(+) + NADPH + O2 = 2'-aminobiphenyl-2,3-diol + NADP(+) Binds 1 [2Fe-2S] cluster per subunit. Optimum pH is between 7 and 7.5. Optimum temperature is 30 degrees Celsius. Homotrimer. Carbazole 1,9a-dioxygenase complex consists of a terminal oxygenase component CarAa, a ferredoxin reductase component CarAd and a ferredoxin component CarAc.