Reductase component of a two-component system involved in the biosynthesis of the enediyne antitumor antibiotic C-1027 (PubMed:18426211, PubMed:19817865). SgcE6 provides the FADH(2) required by both the halogenase SgcC3 and the monooxygenase SgcC through free diffusion (PubMed:18426211, PubMed:19817865). Accepts only NADH and FAD as substrates (PubMed:19817865). FADH2 + NAD(+) = FAD + 2 H(+) + NADH The SgcE6-SgcC hydroxylation activity decreases in the presence of excess FAD. kcat is 3.1 sec(-1) with NADH as substrate. kcat is 4.5 sec(-1) with FAD as substrate. Antibiotic biosynthesis. Homodimer. Belongs to the non-flavoprotein flavin reductase family.