N-carbamoyl L-aspartate + H+ <=> (S)-dihydroorotate + H2O Authored: Jassal, B, 2003-06-17 09:00:25 EC Number: 3.5.2.3 Edited: D'Eustachio, P, 0000-00-00 00:00:00 Pubmed8619816 Reactome Database ID Release 4373571 Reactome, http://www.reactome.org ReactomeREACT_744 The synthesis of dihydroorotate from N-carbamoyl L-aspartate is catalyzed by the dihydroorotase activity of cytosolic trifunctional CAD (carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase) protein. This activity has not been directly demonstrated in experimental studies of the purified human protein, but has been inferred from the behavior of the purified hamster protein and the high degree of sequence similarity between the cloned hamster and human genes (Iwahana et al. 1996). Also on the basis of this similarity, the active human protein is annotated as a hexamer (Lee et al. 1985). condensation of N-Carbamoyl-L-aspartate to form (S)-Dihydroorotate (ring closure)