Biphenyl 2,3-dioxygenase  In enzymology, a biphenyl 2,3-dioxygenase () is an enzyme that catalyzes the chemical reaction  The 4 substrates of this enzyme are biphenyl, NADH, H+, and O2, whereas its two products are (1S,2R)-3-phenylcyclohexa-3,5-diene-1,2-diol and NAD+. This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with NADH or NADPH as one donor, and incorporation of two atoms o oxygen into the other donor. The systematic name of this enzyme class is biphenyl,NADH:oxygen oxidoreductase (2,3-hydroxylating). This enzyme is also called biphenyl dioxygenase. This enzyme participates in biphenyl degradation. As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and .