5-Amino-6-ribitylamino uracil is an intermediate in riboflavin metabolism. It is converted from 5-Amino-6-(5'-phosphoribitylamino)uracil via dephosphorylation by the enzyme phosphohistidine phosphatase 1 (EC 3. 1. 3. -). It is considered to be the second product of the riboflavin synthase reaction (PMID: 14245407). Humans do not have all the enzymes needed to synthesize or metabolize riboflavin. However, gut microflora do have the necessary enzymatic machinery to produce and metabolize this vitamin. Riboflavin (or vitamin B2) is an easily absorbed micronutrient with a key role in maintaining health in humans and animals. It is the central component of the cofactors FAD and FMN, and is therefore required by all flavoproteins. Riboflavin is yellow or yellow-orange in color and in addition to being used as a food coloring it is also used to fortify some foods including baby foods, breakfast cereals, pastas, sauces, processed cheese, fruit drinks, vitamin-enriched milk products, some energy drinks, and vitamin supplements.