Degrades exclusively diarylether compounds having carboxyl groups in the 3- or 4-position. Yields a hemiacetal that spontaneously hydrolyzes to phenol and protocatechuate. Binds 1 [2Fe-2S] cluster. Binds 1 Fe cation. Aromatic compound metabolism; carboxydiphenyl ether degradation. This dioxygenase system consists of two proteins: the alpha subunit (PobA) and a subunit (PobB) that acts as a ferredoxin and a ferredoxin reductase. By 3- or 4-carboxydiphenyl ether and by phenol. Belongs to the bacterial ring-hydroxylating dioxygenase alpha subunit family.