Catalyzes the meta-cleavage of the hydroxylated biphenyl ring. The enzyme can oxidize a wide range of substrates, and the substrate preference order is 2,3-dihydroxybiphenyl > 3-methylcatechol > catechol > 4-methylcatechol > 4-chlorocatechol. biphenyl-2,3-diol + O2 = 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate + H(+) Binds 1 Mn(2+) ion per subunit. Optimum pH is 7.5. Optimum temperature is 85 degrees Celsius. Xenobiotic degradation; biphenyl degradation; 2-hydroxy-2,4-pentadienoate and benzoate from biphenyl: step 3/4. Homotetramer. Belongs to the extradiol ring-cleavage dioxygenase family.