. "Catalysis of the reaction: diphosphate + UMP = 5-phospho-alpha-D-ribose 1-diphosphate + uracil." . . "uracil phosphoribosyltransferase activity" . "UMP diphosphorylase activity" . "UMP pyrophosphorylase activity" . "UMP:diphosphate phospho-alpha-D-ribosyltransferase activity" . "UMP:pyrophosphate phosphoribosyltransferase activity" . "UPRTase activity" . "uridine 5'-phosphate pyrophosphorylase activity" . "uridine monophosphate pyrophosphorylase activity" . "uridylate pyrophosphorylase activity" . "uridylic pyrophosphorylase activity" . . .