The beta subunit may be responsible for the substrate specificity of the enzyme. biphenyl + H(+) + NADH + O2 = (2R,3S)-3-phenylcyclohexa-3,5-diene-1,2-diol + NAD(+) Xenobiotic degradation; biphenyl degradation; 2-hydroxy-2,4-pentadienoate and benzoate from biphenyl: step 1/4. Heterohexamer consisting of 3 BphA1 subunits and 3 BphA2 subunits. A ferredoxin (BphA3) and a ferredoxin reductase (BphA4) must be present to obtain activity. Belongs to the bacterial ring-hydroxylating dioxygenase beta subunit family.