A ring closing reaction generates L dihydroorotate, which is then oxidized to form orotate(乳清酸) in a reaction catalyzed by dihydroorotate dehydrogenase Orotate is then linked to prpp to form orotidylate, which is then converted to UMP by a decarboxylation reaction CTP is derived from utp by accepting an amino group from gIn or Nh4+ In eukaryotic cells, carbamoyl phosphate synthetase Il, aspartate transcarbamoylase dihydroorotase, and are part of a trifunctional proteins called CAD• A ring closing reaction generates L￾dihydroorotate, which is then oxidized to form orotate (乳清酸) in a reaction catalyzed by dihydroorotate dehydrogenase. • Orotate is then linked to PRPP to form orotidylate, which is then converted to UMP by a decarboxylation reaction. • CTP is derived from UTP by accepting an amino group from Gln or NH4 +. • In eukaryotic cells, carbamoyl phosphate synthetase II, aspartate transcarbamoylase, dihydroorotase, and are part of a trifunctional proteins called CAD