Shows a preference for catechols with groups immediately adjacent to the hydroxyl substituents. biphenyl-2,3-diol + O2 = 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate + H(+) Binds 1 Fe(2+) ion per subunit. Substrate inhibition occurs at 300 uM (+/- 20 uM). Optimum pH is 8.0. Xenobiotic degradation; biphenyl degradation; 2-hydroxy-2,4-pentadienoate and benzoate from biphenyl: step 3/4. Homooctamer. The enzyme is composed of two planar tetramers rotated at 45 degrees relative to each other, with a channel in the middle. Belongs to the extradiol ring-cleavage dioxygenase family.