Flad1 has 2 isoforms, one predicted to be cytosolic (Flad1-PB) and one predicted to be mitochondrial (Flad1-PA) suggesting that FAD synthesis can occur in the mitochondrion. Unlike human FLAD1, Flad1 lacks the domain that has FAD diphosphatase activity and therefore cannot convert FAD back to FMN. It is unclear whether D. melanogaster can convert FAD and FMN back to FMN and riboflavin, respectively. Potential riboflavin, FMN and FAD mitochondrial transporters have not been characterised, yet. Flad2 is a paralog of Flad1 and is specifically expressed in testis. As there is no functional information, Flad2 is not included in the gene list.