FAD synthase (FMN:ATP adenylyl transferase (FMNAT); FAD pyrophosphorylase; Flavin adenine dinucleotide synthase (FADS); EC 2.7.7.2) is involved in the biochemical pathway for converting riboflavin into FAD. By sequence comparison, bacterial and eukaryotic FMNAT enzymes belong to two different protein superfamilies and apparently utilize different sets of active-site residues to accomplish the same chemistry. This subfamily includes eukaryotic FMNATs, which are members of the 3'-phosphoadenosine 5'-phosphosulfate (PAPS) reductase-like family belonging to the adenine nucleotide alpha hydrolase superfamily, which has conserved motifs different from those of nucleotidylyl transferases.
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