FLAD1 is a 587 amino acid protein where its N-terminus belongs to the moaB/mog family and its C-terminus belongs to the PAPS reductase family. Existing as five alternatively spliced isoforms, FLAD1 localizes to the cytoplasm and utilizes magnesium as a cofactor. FLAD1 is a key enzyme in the metabolic pathway that converts riboflavin into the redox cofactor flavin adenine dinucleotide (FAD). It is suggested that the molybdenum cofactor biosynthesis protein-like region of FLAD1 may not be functional.