Involved in the gamma-resorcylate (2,6-dihydroxybenzoate) catabolism (PubMed:17158677). Reductase component of the resorcinol hydroxylase, which catalyzes the FADPH-dependent conversion of resorcinol to hydroxyquinol (PubMed:17158677). Catalyzes the reduction of FAD by NADH. The reduced flavin is then transferred to the oxygenase component GraA (PubMed:17158677). FADH2 + NAD(+) = FAD + 2 H(+) + NADH Aromatic compound metabolism. The FADH(2)-dependent resorcinol hydroxylase is composed of two subunits, GraA (the oxygenase component) and GraD (the reductase component). Both subunits are required for activity. Induced in the presence of gamma-resorcylate. Belongs to the non-flavoprotein flavin reductase family.