description | Protein involved in the synthesis of riboflavin (Vitamin B2), which consists of ribose attached to a flavin moiety. It is synthesized by all green plants and most microorganisms and occurs free in milk, the retina, whey and urine. It is found in most cells as a component of the coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) |