Facilitates the conversion of 5-amino-6-(5'-phosphoribosylamino)uracil to 5-amino-6-(5'-phosphoribitylamino)uracil.
Faciliates the conversion of 2,5-diamino-6-(ribosylamino)-4-(3H)-pyrimidinone 5'-phosphate to 5-amino-6-(5'-phosphoribosylamino)uracil.