Involved in pyrimidine base degradation. Catalyzes the reduction of uracil and thymine. 5,6-dihydrouracil + NADP(+) = H(+) + NADPH + uracil 5,6-dihydrothymine + NADP(+) = H(+) + NADPH + thymine Binds 2 FAD. Binds 2 FMN. Binds 4 [4Fe-4S] clusters. Contains approximately 16 iron atoms per subunit. Inactivated by 5-iodouracil. Amino-acid biosynthesis; beta-alanine biosynthesis. Homodimer. Belongs to the dihydropyrimidine dehydrogenase family.