<p>Members of this family occur as the BphD protein of biphenyl catabolism and as the TodD protein of toluene catabolism. Members catalyse the second step in each pathway and proved interchangeable when tested; the first and fourth enzymes in each pathway confer metabolic specificity. In the context of biphenyl degradation, the enzyme acts as cis-2,3-dihydrobiphenyl-2,3-diol dehydrogenase (<db_xref db="EC" dbkey="1.3.1.56"/>), while in toluene degradation it acts as cis-toluene dihydrodiol dehydrogenase.</p>