biphenyl-2,3-diol + O2 = 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate + H(+) Xenobiotic degradation; biphenyl degradation; 2-hydroxy-2,4-pentadienoate and benzoate from biphenyl: step 3/4. Belongs to the extradiol ring-cleavage dioxygenase family.