Catalyzes the reversible cyclization of carbamoyl aspartate to dihydroorotate. (S)-dihydroorotate + H2O = H(+) + N-carbamoyl-L-aspartate Binds 2 Zn(2+) ions per subunit (PubMed:6142052, PubMed:11401542, PubMed:15826651). In vitro, can also use Co(2+) or Cd(2+) (PubMed:1671037, PubMed:15610022). kcat is 127 sec(-1) with dihydroorotate as substrate and 195 sec(-1) with N-carbamoyl-DL-aspartate as substrate (PubMed:6142052). kcat is 100 sec(-1) with dihydroorotate as substrate and 160 sec(-1) with carbamoyl aspartate as substrate in the presence of Zn(2+). kcat is 15 sec(-1) with dihydroorotate as substrate and 25 sec(-1) with carbamoyl aspartate as substrate in the presence of Co(2+). kcat is 1.9 sec(-1) with dihydroorotate as substrate and 8.2 sec(-1) with carbamoyl aspartate as substrate in the presence of Cd(2+) (PubMed:15610022). Pyrimidine metabolism; UMP biosynthesis via de novo pathway; (S)-dihydroorotate from bicarbonate: step 3/3. Homodimer. Induced by pyrimidine limitation. There is an asymmetry between active sites in the dimer, with dihydroorotate bound to the active site of subunit A and N-carbamoyl-L-aspartate bound to the active site of subunit B. Belongs to the metallo-dependent hydrolases superfamily. DHOase family. Class II DHOase subfamily.