carbamoyl phosphate + L-aspartate = H(+) + N-carbamoyl-L-aspartate + phosphate Pyrimidine metabolism; UMP biosynthesis via de novo pathway; (S)-dihydroorotate from bicarbonate: step 2/3. Heterooligomer of catalytic and regulatory chains. Belongs to the aspartate/ornithine carbamoyltransferase superfamily. ATCase family.