Molecular function

OPRT activity, OPRTase activity, orotate phosphoribosyl pyrophosphate transferase activity, orotic acid phosphoribosyltransferase activity, orotidine 5'-monophosphate pyrophosphorylase activity, orotidine monophosphate pyrophosphorylase activity, orotidine phosphoribosyltransferase activity, orotidine-5'-phosphate diphosphorylase activity, orotidine-5'-phosphate pyrophosphorylase activity, orotidine-5'-phosphate:diphosphate phospho-alpha-D-ribosyl-transferase activity, orotidylate phosphoribosyltransferase activity, orotidylate pyrophosphorylase activity, orotidylic acid phosphorylase activity, orotidylic acid pyrophosphorylase activity, orotidylic phosphorylase activity, orotidylic pyrophosphorylase activity

Catalysis of the reaction: orotidine 5'-phosphate + diphosphate = orotate + 5-phospho-alpha-D-ribose 1-diphosphate.