Reaction catalyzed by diaminohydroxyphosphoribosylaminopyrimidine deaminase (3.5.4.26)

		+		H2O	=			+		NH3
	2,5-diamino-6-hydroxy-4-(5-phospho-D-ribosylamino)pyrimidine	+		H2O	=		5-amino-6-(5-phospho-D-ribosylamino)uracil	+		NH3