Catalyzes the synthesis of 5,6-dihydrouridine (D), a modified base found in the D-loop of most tRNAs, via the reduction of the C5-C6 double bond in target uridines. DusC specifically modifies U16 in tRNAs. 5,6-dihydrouridine(16) in tRNA + NADP(+) = H(+) + NADPH + uridine(16) in tRNA 5,6-dihydrouridine(16) in tRNA + NAD(+) = H(+) + NADH + uridine(16) in tRNA Is composed of two domains: an N-terminal catalytic domain (residues 1-242) and a C-terminal tRNA recognition domain (residues 245-309). A dusA dusB dusC triple mutant exhibits a complete lack of 5,6-dihydrouridine modification in cellular tRNA, whereas each single mutant exhibits a partial reduction, compared to wild type. DusB and DusC together account for about half of the 5,6-dihydrouridine modification observed in wild-type cellular tRNA, and DusA accounts for the other half. These three enzymes seem to act site-specifically on the tRNA D-loop and contain nonredundant catalytic functions in vivo. Belongs to the Dus family. DusC subfamily.