Catalyzes the meta-cleavage of 3,4-dihydroxy-9,10-seconandrost-1,3,5(10)-triene-9,17-dione (3,4-DHSA) to produce 4,5-9,10-diseco-3-hydroxy-5,9,17-trioxoandrosta-1(10),2-diene-4-oic acid (4,9-DSHA). Also involved in biphenyl and polychlorinated biphenyls (PCBs) degradation. 3,4-dihydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione + O2 = (1E,2Z)-3-hydroxy-5,9,17-trioxo-4,5:9,10-disecoandrosta-1(10),2-dien-4-oate + H(+) Binds 1 Fe(2+) ion per subunit. Steroid metabolism; cholesterol metabolism. Homodimer. Cells lacking this gene grow on cholesterol at a rate that is 60% that of the wild-type and develop a pink color consistent with the accumulation and nonenzymatic oxidation of a catechol. Belongs to the extradiol ring-cleavage dioxygenase family.