The cofactors FMN and FAD participate in numerous processes in all organisms, including mitochondrial electron transport, photosynthesis, fatty-acid oxidation, and metabolism of vitamin B6, vitamin B12 and folates . While monofunctional riboflavin kinase is found in eukaryotes, some bacteria have a bifunctional enzyme that exhibits both this activity and that of EC 18.104.22.168
, FMN adenylyltransferase . A divalent metal cation is required for activity (with different species preferring Mg2+, Mn2+ or Zn2+). In Bacillus subtilis, ATP can be replaced by other phosphate donors but with decreasing enzyme activity in the order ATP > dATP > CTP > UTP .