In enzymology, 5-amino-6-(5-phosphoribosylamino)uracil reductase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are 5-amino-6-(5-phospho-D-ribitylamino)uracil and oxidised nicotinamide adenine dinucleotide phosphate (NADP<sup>+</sup>). Its products are 5-amino-6-(5-phospho-ò-D-ribosylamino)uracil, reduced NADPH, and a proton.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD<sup>+</sup> or NADP<sup>+</sup> as acceptor. The systematic name of this enzyme class is 5-amino-6-(5-phosphoribitylamino)uracil:NADP<sup>+</sup> 1'-oxidoreductase. This enzyme is also called aminodioxyphosphoribosylaminopyrimidine reductase. This enzyme participates in riboflavin metabolism.
As of late 2007, 7 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , and .