Anti-riboflavin kinase antibodies are used in the immunodetection of the protein encoded by the RFK gene. In humans, the canonical protein has a reported length of 155 amino acid residues and a mass of 17.6 kDa. Its subcellular localization is in the cytoplasm. It is notably expressed in the brain, placenta and urinary bladder. It is known to catalyze the phosphorylation of riboflavin (vitamin B2) to form flavin-mononucleotide (FMN), hence rate-limiting enzyme in the synthesis of FAD. Other names for this target antigen include 0610038L10Rik, ATP:riboflavin 5'-phosphotransferase, flavokinase, and RIFK.