Anaerobic sulfite reductase contains an FAD and NADPH binding module with structural similarity to ferredoxin reductase and sequence similarity to dihydroorotate dehydrogenases. Clostridium pasteurianum inducible dissimilatory type sulfite reductase is linked to ferredoxin and reduces NH2OH and SeO3 at a lesser rate than it's normal substate SO3(2-). Dihydroorotate dehydrogenases (DHODs) catalyze the only redox reaction in pyrimidine de novo biosynthesis. They catalyze the oxidation of (S)-dihydroorotate to orotate coupled with the reduction of NAD+.
Jiyao W et al.(2023). "The conserved domain database in 2023.",